diff --git a/validator_client/src/config.rs b/validator_client/src/config.rs
index 104a4bbe6..68405ed2f 100644
--- a/validator_client/src/config.rs
+++ b/validator_client/src/config.rs
@@ -1,11 +1,13 @@
 use std::fs;
 use std::path::PathBuf;
+use types::ChainSpec;
 
 /// Stores the core configuration for this validator instance.
 #[derive(Clone)]
 pub struct ClientConfig {
     pub data_dir: PathBuf,
     pub server: String,
+    pub spec: ChainSpec,
 }
 
 const DEFAULT_LIGHTHOUSE_DIR: &str = ".lighthouse-validators";
@@ -20,6 +22,11 @@ impl ClientConfig {
         fs::create_dir_all(&data_dir)
             .unwrap_or_else(|_| panic!("Unable to create {:?}", &data_dir));
         let server = "localhost:50051".to_string();
-        Self { data_dir, server }
+        let spec = ChainSpec::foundation();
+        Self {
+            data_dir,
+            server,
+            spec,
+        }
     }
 }
diff --git a/validator_client/src/main.rs b/validator_client/src/main.rs
index c835300b5..4344bc16e 100644
--- a/validator_client/src/main.rs
+++ b/validator_client/src/main.rs
@@ -43,6 +43,16 @@ fn main() {
                 .help("Address to connect to BeaconNode.")
                 .takes_value(true),
         )
+        .arg(
+            Arg::with_name("spec")
+                .long("spec")
+                .value_name("spec")
+                .short("s")
+                .help("Configuration of Beacon Chain")
+                .takes_value(true)
+                .possible_values(&["foundation", "few_validators"])
+                .default_value("foundation"),
+        )
         .get_matches();
 
     let mut config = ClientConfig::default();
@@ -62,6 +72,17 @@ fn main() {
         }
     }
 
+    // TODO: Permit loading a custom spec from file.
+    // Custom spec
+    if let Some(spec_str) = matches.value_of("spec") {
+        match spec_str {
+            "foundation" => config.spec = ChainSpec::foundation(),
+            "few_validators" => config.spec = ChainSpec::few_validators(),
+            // Should be impossible due to clap's `possible_values(..)` function.
+            _ => unreachable!(),
+        };
+    }
+
     // Log configuration
     info!(log, "";
           "data_dir" => &config.data_dir.to_str(),
@@ -81,11 +102,8 @@ fn main() {
         Arc::new(ValidatorServiceClient::new(ch))
     };
 
-    // Ethereum
-    //
-    // TODO: Permit loading a custom spec from file.
-    // https://github.com/sigp/lighthouse/issues/160
-    let spec = Arc::new(ChainSpec::foundation());
+    // Spec
+    let spec = Arc::new(config.spec.clone());
 
     // Clock for determining the present slot.
     // TODO: this shouldn't be a static time, instead it should be pulled from the beacon node.