diff --git a/beacon_node/Cargo.toml b/beacon_node/Cargo.toml
index e5893195e..4a930cfd2 100644
--- a/beacon_node/Cargo.toml
+++ b/beacon_node/Cargo.toml
@@ -14,6 +14,7 @@ clap = "2.32.0"
 db = { path = "db" }
 dirs = "1.0.3"
 futures = "0.1.23"
+fork_choice = { path = "../eth2/fork_choice" }
 genesis = { path = "../eth2/genesis" }
 slog = "^2.2.3"
 slot_clock = { path = "../eth2/utils/slot_clock" }
diff --git a/beacon_node/beacon_chain/src/beacon_chain.rs b/beacon_node/beacon_chain/src/beacon_chain.rs
index 3a44fbda5..f97b42b78 100644
--- a/beacon_node/beacon_chain/src/beacon_chain.rs
+++ b/beacon_node/beacon_chain/src/beacon_chain.rs
@@ -54,9 +54,9 @@ pub enum InvalidBlock {
 
 #[derive(Debug, PartialEq)]
 pub enum BlockProcessingOutcome {
-    /// The block was sucessfully validated.
+    /// The block was successfully validated.
     ValidBlock(ValidBlock),
-    /// The block was not sucessfully validated.
+    /// The block was not successfully validated.
     InvalidBlock(InvalidBlock),
 }
 
@@ -70,7 +70,7 @@ pub struct BeaconChain<T: ClientDB + Sized, U: SlotClock, F: ForkChoice> {
     justified_head: RwLock<CheckPoint>,
     pub state: RwLock<BeaconState>,
     pub spec: ChainSpec,
-    pub fork_choice: F,
+    pub fork_choice: RwLock<F>,
 }
 
 impl<T, U, F> BeaconChain<T, U, F>
@@ -129,7 +129,7 @@ where
             finalized_head,
             canonical_head,
             spec,
-            fork_choice,
+            fork_choice: RwLock::new(fork_choice),
         })
     }
 
@@ -331,7 +331,7 @@ where
     /// - Create a new `Attestation`.
     /// - Aggregate it to an existing `Attestation`.
     pub fn process_free_attestation(
-        &mut self,
+        &self,
         free_attestation: FreeAttestation,
     ) -> Result<AggregationOutcome, Error> {
         let aggregation_outcome = self
@@ -347,7 +347,7 @@ where
         }
 
         // valid attestation, proceed with fork-choice logic
-        self.fork_choice.add_attestation(
+        self.fork_choice.write().add_attestation(
             free_attestation.validator_index,
             &free_attestation.data.beacon_block_root,
         )?;
@@ -408,7 +408,7 @@ where
     /// Accept some block and attempt to add it to block DAG.
     ///
     /// Will accept blocks from prior slots, however it will reject any block from a future slot.
-    pub fn process_block(&mut self, block: BeaconBlock) -> Result<BlockProcessingOutcome, Error> {
+    pub fn process_block(&self, block: BeaconBlock) -> Result<BlockProcessingOutcome, Error> {
         debug!("Processing block with slot {}...", block.slot());
 
         let block_root = block.canonical_root();
@@ -479,7 +479,7 @@ where
         self.state_store.put(&state_root, &ssz_encode(&state)[..])?;
 
         // run the fork_choice add_block logic
-        self.fork_choice.add_block(&block, &block_root)?;
+        self.fork_choice.write().add_block(&block, &block_root)?;
 
         // If the parent block was the parent_block, automatically update the canonical head.
         //
@@ -501,7 +501,7 @@ where
 
     /// Produce a new block at the present slot.
     ///
-    /// The produced block will not be inheriently valid, it must be signed by a block producer.
+    /// The produced block will not be inherently valid, it must be signed by a block producer.
     /// Block signing is out of the scope of this function and should be done by a separate program.
     pub fn produce_block(&self, randao_reveal: Signature) -> Option<(BeaconBlock, BeaconState)> {
         debug!("Producing block at slot {}...", self.state.read().slot);
@@ -559,10 +559,10 @@ where
     }
 
     // TODO: Left this as is, modify later
-    pub fn fork_choice(&mut self) -> Result<(), Error> {
+    pub fn fork_choice(&self) -> Result<(), Error> {
         let present_head = self.finalized_head().beacon_block_root;
 
-        let new_head = self.fork_choice.find_head(&present_head)?;
+        let new_head = self.fork_choice.write().find_head(&present_head)?;
 
         if new_head != present_head {
             let block = self
diff --git a/beacon_node/beacon_chain/test_harness/src/harness.rs b/beacon_node/beacon_chain/test_harness/src/harness.rs
index 010ba8f85..533bfe4f6 100644
--- a/beacon_node/beacon_chain/test_harness/src/harness.rs
+++ b/beacon_node/beacon_chain/test_harness/src/harness.rs
@@ -5,7 +5,7 @@ use db::{
     stores::{BeaconBlockStore, BeaconStateStore},
     MemoryDB,
 };
-use fork_choice::*; // import all the algorithms
+use fork_choice::{optimised_lmd_ghost::OptimisedLMDGhost, slow_lmd_ghost::SlowLMDGhost}; // import all the algorithms
 use log::debug;
 use rayon::prelude::*;
 use slot_clock::TestingSlotClock;
@@ -40,8 +40,8 @@ impl BeaconChainHarness {
         let db = Arc::new(MemoryDB::open());
         let block_store = Arc::new(BeaconBlockStore::new(db.clone()));
         let state_store = Arc::new(BeaconStateStore::new(db.clone()));
-
         let slot_clock = TestingSlotClock::new(spec.genesis_slot);
+        let fork_choice = OptimisedLMDGhost::new(block_store.clone(), state_store.clone());
 
         // Remove the validators present in the spec (if any).
         spec.initial_validators = Vec::with_capacity(validator_count);
@@ -83,6 +83,7 @@ impl BeaconChainHarness {
                 block_store.clone(),
                 slot_clock,
                 spec.clone(),
+                fork_choice,
             )
             .unwrap(),
         );
@@ -200,7 +201,7 @@ impl BeaconChainHarness {
         // Produce a new block.
         let block = self.produce_block();
         debug!("Submitting block for processing...");
-        self.beacon_chain.process_block(block).unwrap();
+        &mut (self.beacon_chain).process_block(block).unwrap();
         debug!("...block processed by BeaconChain.");
 
         debug!("Producing free attestations...");
diff --git a/beacon_node/beacon_chain/test_harness/src/validator/direct_beacon_node.rs b/beacon_node/beacon_chain/test_harness/src/validator/direct_beacon_node.rs
index ed71f28d3..d33f782d6 100644
--- a/beacon_node/beacon_chain/test_harness/src/validator/direct_beacon_node.rs
+++ b/beacon_node/beacon_chain/test_harness/src/validator/direct_beacon_node.rs
@@ -8,6 +8,7 @@ use block_producer::{
     PublishOutcome as BlockPublishOutcome,
 };
 use db::ClientDB;
+use fork_choice::ForkChoice;
 use parking_lot::RwLock;
 use slot_clock::SlotClock;
 use std::sync::Arc;
@@ -22,14 +23,14 @@ use types::{AttestationData, BeaconBlock, FreeAttestation, PublicKey, Signature}
 /// `BeaconBlock`s and `FreeAttestation`s are not actually published to the `BeaconChain`, instead
 /// they are stored inside this struct. This is to allow one to benchmark the submission of the
 /// block/attestation directly, or modify it before submission.
-pub struct DirectBeaconNode<T: ClientDB, U: SlotClock> {
-    beacon_chain: Arc<BeaconChain<T, U>>,
+pub struct DirectBeaconNode<T: ClientDB, U: SlotClock, F: ForkChoice> {
+    beacon_chain: Arc<BeaconChain<T, U, F>>,
     published_blocks: RwLock<Vec<BeaconBlock>>,
     published_attestations: RwLock<Vec<FreeAttestation>>,
 }
 
-impl<T: ClientDB, U: SlotClock> DirectBeaconNode<T, U> {
-    pub fn new(beacon_chain: Arc<BeaconChain<T, U>>) -> Self {
+impl<T: ClientDB, U: SlotClock, F: ForkChoice> DirectBeaconNode<T, U, F> {
+    pub fn new(beacon_chain: Arc<BeaconChain<T, U, F>>) -> Self {
         Self {
             beacon_chain,
             published_blocks: RwLock::new(vec![]),
@@ -48,7 +49,7 @@ impl<T: ClientDB, U: SlotClock> DirectBeaconNode<T, U> {
     }
 }
 
-impl<T: ClientDB, U: SlotClock> AttesterBeaconNode for DirectBeaconNode<T, U> {
+impl<T: ClientDB, U: SlotClock, F: ForkChoice> AttesterBeaconNode for DirectBeaconNode<T, U, F> {
     fn produce_attestation_data(
         &self,
         _slot: u64,
@@ -69,7 +70,7 @@ impl<T: ClientDB, U: SlotClock> AttesterBeaconNode for DirectBeaconNode<T, U> {
     }
 }
 
-impl<T: ClientDB, U: SlotClock> BeaconBlockNode for DirectBeaconNode<T, U> {
+impl<T: ClientDB, U: SlotClock, F: ForkChoice> BeaconBlockNode for DirectBeaconNode<T, U, F> {
     /// Requests the `proposer_nonce` from the `BeaconChain`.
     fn proposer_nonce(&self, pubkey: &PublicKey) -> Result<u64, BeaconBlockNodeError> {
         let validator_index = self
diff --git a/beacon_node/beacon_chain/test_harness/src/validator/direct_duties.rs b/beacon_node/beacon_chain/test_harness/src/validator/direct_duties.rs
index e724b3e55..c6d97ee37 100644
--- a/beacon_node/beacon_chain/test_harness/src/validator/direct_duties.rs
+++ b/beacon_node/beacon_chain/test_harness/src/validator/direct_duties.rs
@@ -6,19 +6,20 @@ use block_producer::{
     DutiesReader as ProducerDutiesReader, DutiesReaderError as ProducerDutiesReaderError,
 };
 use db::ClientDB;
+use fork_choice::ForkChoice;
 use slot_clock::SlotClock;
 use std::sync::Arc;
 use types::PublicKey;
 
 /// Connects directly to a borrowed `BeaconChain` and reads attester/proposer duties directly from
 /// it.
-pub struct DirectDuties<T: ClientDB, U: SlotClock> {
-    beacon_chain: Arc<BeaconChain<T, U>>,
+pub struct DirectDuties<T: ClientDB, U: SlotClock, F: ForkChoice> {
+    beacon_chain: Arc<BeaconChain<T, U, F>>,
     pubkey: PublicKey,
 }
 
-impl<T: ClientDB, U: SlotClock> DirectDuties<T, U> {
-    pub fn new(pubkey: PublicKey, beacon_chain: Arc<BeaconChain<T, U>>) -> Self {
+impl<T: ClientDB, U: SlotClock, F: ForkChoice> DirectDuties<T, U, F> {
+    pub fn new(pubkey: PublicKey, beacon_chain: Arc<BeaconChain<T, U, F>>) -> Self {
         Self {
             beacon_chain,
             pubkey,
@@ -26,7 +27,7 @@ impl<T: ClientDB, U: SlotClock> DirectDuties<T, U> {
     }
 }
 
-impl<T: ClientDB, U: SlotClock> ProducerDutiesReader for DirectDuties<T, U> {
+impl<T: ClientDB, U: SlotClock, F: ForkChoice> ProducerDutiesReader for DirectDuties<T, U, F> {
     fn is_block_production_slot(&self, slot: u64) -> Result<bool, ProducerDutiesReaderError> {
         let validator_index = self
             .beacon_chain
@@ -41,7 +42,7 @@ impl<T: ClientDB, U: SlotClock> ProducerDutiesReader for DirectDuties<T, U> {
     }
 }
 
-impl<T: ClientDB, U: SlotClock> AttesterDutiesReader for DirectDuties<T, U> {
+impl<T: ClientDB, U: SlotClock, F: ForkChoice> AttesterDutiesReader for DirectDuties<T, U, F> {
     fn validator_index(&self) -> Option<u64> {
         match self.beacon_chain.validator_index(&self.pubkey) {
             Some(index) => Some(index as u64),
diff --git a/beacon_node/beacon_chain/test_harness/src/validator/validator.rs b/beacon_node/beacon_chain/test_harness/src/validator/validator.rs
index d33a0412b..2e9b4e981 100644
--- a/beacon_node/beacon_chain/test_harness/src/validator/validator.rs
+++ b/beacon_node/beacon_chain/test_harness/src/validator/validator.rs
@@ -7,6 +7,7 @@ use beacon_chain::BeaconChain;
 use block_producer::PollOutcome as BlockPollOutcome;
 use block_producer::{BlockProducer, Error as BlockPollError};
 use db::MemoryDB;
+use fork_choice::{optimised_lmd_ghost::OptimisedLMDGhost, slow_lmd_ghost::SlowLMDGhost};
 use slot_clock::TestingSlotClock;
 use std::sync::Arc;
 use types::{BeaconBlock, ChainSpec, FreeAttestation, Keypair};
@@ -31,20 +32,20 @@ pub enum AttestationProduceError {
 pub struct TestValidator {
     pub block_producer: BlockProducer<
         TestingSlotClock,
-        DirectBeaconNode<MemoryDB, TestingSlotClock>,
-        DirectDuties<MemoryDB, TestingSlotClock>,
+        DirectBeaconNode<MemoryDB, TestingSlotClock, OptimisedLMDGhost<MemoryDB>>,
+        DirectDuties<MemoryDB, TestingSlotClock, OptimisedLMDGhost<MemoryDB>>,
         TestSigner,
     >,
     pub attester: Attester<
         TestingSlotClock,
-        DirectBeaconNode<MemoryDB, TestingSlotClock>,
-        DirectDuties<MemoryDB, TestingSlotClock>,
+        DirectBeaconNode<MemoryDB, TestingSlotClock, OptimisedLMDGhost<MemoryDB>>,
+        DirectDuties<MemoryDB, TestingSlotClock, OptimisedLMDGhost<MemoryDB>>,
         TestSigner,
     >,
     pub spec: Arc<ChainSpec>,
-    pub epoch_map: Arc<DirectDuties<MemoryDB, TestingSlotClock>>,
+    pub epoch_map: Arc<DirectDuties<MemoryDB, TestingSlotClock, OptimisedLMDGhost<MemoryDB>>>,
     pub keypair: Keypair,
-    pub beacon_node: Arc<DirectBeaconNode<MemoryDB, TestingSlotClock>>,
+    pub beacon_node: Arc<DirectBeaconNode<MemoryDB, TestingSlotClock, OptimisedLMDGhost<MemoryDB>>>,
     pub slot_clock: Arc<TestingSlotClock>,
     pub signer: Arc<TestSigner>,
 }
@@ -56,7 +57,7 @@ impl TestValidator {
     /// A `BlockProducer` and `Attester` is created..
     pub fn new(
         keypair: Keypair,
-        beacon_chain: Arc<BeaconChain<MemoryDB, TestingSlotClock>>,
+        beacon_chain: Arc<BeaconChain<MemoryDB, TestingSlotClock, OptimisedLMDGhost<MemoryDB>>>,
         spec: Arc<ChainSpec>,
     ) -> Self {
         let slot_clock = Arc::new(TestingSlotClock::new(spec.genesis_slot));
diff --git a/beacon_node/src/main.rs b/beacon_node/src/main.rs
index 25239a9f6..09471860b 100644
--- a/beacon_node/src/main.rs
+++ b/beacon_node/src/main.rs
@@ -13,6 +13,7 @@ use db::{
     stores::{BeaconBlockStore, BeaconStateStore},
     MemoryDB,
 };
+use fork_choice::optimised_lmd_ghost::OptimisedLMDGhost;
 use slog::{error, info, o, Drain};
 use slot_clock::SystemTimeSlotClock;
 use std::sync::Arc;
@@ -78,10 +79,17 @@ fn main() {
     let slot_clock = SystemTimeSlotClock::new(spec.genesis_time, spec.slot_duration)
         .expect("Unable to load SystemTimeSlotClock");
 
+    // Choose the fork choice
+    let fork_choice = OptimisedLMDGhost::new(block_store.clone(), state_store.clone());
     // Genesis chain
     // TODO: persist chain to storage.
-    let _chain_result =
-        BeaconChain::genesis(state_store.clone(), block_store.clone(), slot_clock, spec);
+    let _chain_result = BeaconChain::genesis(
+        state_store.clone(),
+        block_store.clone(),
+        slot_clock,
+        spec,
+        fork_choice,
+    );
 
     let _server = start_server(log.clone());
 
diff --git a/eth2/fork_choice/src/lib.rs b/eth2/fork_choice/src/lib.rs
index bc5ada720..19ddcb04c 100644
--- a/eth2/fork_choice/src/lib.rs
+++ b/eth2/fork_choice/src/lib.rs
@@ -30,7 +30,7 @@ use types::{BeaconBlock, Hash256};
 /// Defines the interface for Fork Choices. Each Fork choice will define their own data structures
 /// which can be built in block processing through the `add_block` and `add_attestation` functions.
 /// The main fork choice algorithm is specified in `find_head
-pub trait ForkChoice {
+pub trait ForkChoice: Send + Sync {
     /// Called when a block has been added. Allows generic block-level data structures to be
     /// built for a given fork-choice.
     fn add_block(
diff --git a/eth2/fork_choice/src/optimised_lmd_ghost.rs b/eth2/fork_choice/src/optimised_lmd_ghost.rs
index d312b140a..67faaca1c 100644
--- a/eth2/fork_choice/src/optimised_lmd_ghost.rs
+++ b/eth2/fork_choice/src/optimised_lmd_ghost.rs
@@ -62,15 +62,18 @@ impl<T> OptimisedLMDGhost<T>
 where
     T: ClientDB + Sized,
 {
-    pub fn new(block_store: BeaconBlockStore<T>, state_store: BeaconStateStore<T>) -> Self {
+    pub fn new(
+        block_store: Arc<BeaconBlockStore<T>>,
+        state_store: Arc<BeaconStateStore<T>>,
+    ) -> Self {
         OptimisedLMDGhost {
             cache: HashMap::new(),
             ancestors: vec![HashMap::new(); 16],
             latest_attestation_targets: HashMap::new(),
             children: HashMap::new(),
             max_known_height: 0,
-            block_store: Arc::new(block_store),
-            state_store: Arc::new(state_store),
+            block_store,
+            state_store,
         }
     }