diff --git a/eth2/utils/ssz/src/decode/impls.rs b/eth2/utils/ssz/src/decode/impls.rs
index 8a5a36780..4137b5a56 100644
--- a/eth2/utils/ssz/src/decode/impls.rs
+++ b/eth2/utils/ssz/src/decode/impls.rs
@@ -1,5 +1,5 @@
 use super::*;
-use ethereum_types::H256;
+use ethereum_types::{H256, U128, U256};
 
 macro_rules! impl_decodable_for_uint {
     ($type: ident, $bit_size: expr) => {
@@ -85,6 +85,48 @@ impl Decode for H256 {
     }
 }
 
+impl Decode for U256 {
+    fn is_ssz_fixed_len() -> bool {
+        true
+    }
+
+    fn ssz_fixed_len() -> usize {
+        32
+    }
+
+    fn from_ssz_bytes(bytes: &[u8]) -> Result<Self, DecodeError> {
+        let len = bytes.len();
+        let expected = <Self as Decode>::ssz_fixed_len();
+
+        if len != expected {
+            Err(DecodeError::InvalidByteLength { len, expected })
+        } else {
+            Ok(U256::from_little_endian(bytes))
+        }
+    }
+}
+
+impl Decode for U128 {
+    fn is_ssz_fixed_len() -> bool {
+        true
+    }
+
+    fn ssz_fixed_len() -> usize {
+        16
+    }
+
+    fn from_ssz_bytes(bytes: &[u8]) -> Result<Self, DecodeError> {
+        let len = bytes.len();
+        let expected = <Self as Decode>::ssz_fixed_len();
+
+        if len != expected {
+            Err(DecodeError::InvalidByteLength { len, expected })
+        } else {
+            Ok(U128::from_little_endian(bytes))
+        }
+    }
+}
+
 macro_rules! impl_decodable_for_u8_array {
     ($len: expr) => {
         impl Decode for [u8; $len] {
diff --git a/eth2/utils/ssz/src/encode/impls.rs b/eth2/utils/ssz/src/encode/impls.rs
index 07886d68f..1202d81fd 100644
--- a/eth2/utils/ssz/src/encode/impls.rs
+++ b/eth2/utils/ssz/src/encode/impls.rs
@@ -1,5 +1,5 @@
 use super::*;
-use ethereum_types::H256;
+use ethereum_types::{H256, U128, U256};
 
 macro_rules! impl_encodable_for_uint {
     ($type: ident, $bit_size: expr) => {
@@ -77,6 +77,42 @@ impl Encode for H256 {
     }
 }
 
+impl Encode for U256 {
+    fn is_ssz_fixed_len() -> bool {
+        true
+    }
+
+    fn ssz_fixed_len() -> usize {
+        32
+    }
+
+    fn ssz_append(&self, buf: &mut Vec<u8>) {
+        let n = <Self as Encode>::ssz_fixed_len();
+        let s = buf.len();
+
+        buf.resize(s + n, 0);
+        self.to_little_endian(&mut buf[s..]);
+    }
+}
+
+impl Encode for U128 {
+    fn is_ssz_fixed_len() -> bool {
+        true
+    }
+
+    fn ssz_fixed_len() -> usize {
+        16
+    }
+
+    fn ssz_append(&self, buf: &mut Vec<u8>) {
+        let n = <Self as Encode>::ssz_fixed_len();
+        let s = buf.len();
+
+        buf.resize(s + n, 0);
+        self.to_little_endian(&mut buf[s..]);
+    }
+}
+
 macro_rules! impl_encodable_for_u8_array {
     ($len: expr) => {
         impl Encode for [u8; $len] {
diff --git a/tests/ef_tests/Cargo.toml b/tests/ef_tests/Cargo.toml
index 367cbbe14..8a5cc4372 100644
--- a/tests/ef_tests/Cargo.toml
+++ b/tests/ef_tests/Cargo.toml
@@ -5,6 +5,9 @@ authors = ["Paul Hauner <paul@paulhauner.com>"]
 edition = "2018"
 
 [dependencies]
+ethereum-types = "0.5"
+hex = "0.3"
 serde = "1.0"
 serde_derive = "1.0"
 serde_yaml = "0.8"
+ssz = { path = "../../eth2/utils/ssz" }
diff --git a/tests/ef_tests/src/error.rs b/tests/ef_tests/src/error.rs
new file mode 100644
index 000000000..58732e83e
--- /dev/null
+++ b/tests/ef_tests/src/error.rs
@@ -0,0 +1,9 @@
+#[derive(Debug, PartialEq, Clone)]
+pub enum Error {
+    /// The value in the test didn't match our value.
+    NotEqual(String),
+    /// The test specified a failure and we did not experience one.
+    DidntFail(String),
+    /// Failed to parse the test (internal error).
+    FailedToParseTest(String),
+}
diff --git a/tests/ef_tests/src/lib.rs b/tests/ef_tests/src/lib.rs
index f7308c32b..828e2615c 100644
--- a/tests/ef_tests/src/lib.rs
+++ b/tests/ef_tests/src/lib.rs
@@ -1,4 +1,12 @@
+use error::Error;
 use serde_derive::Deserialize;
+use ssz::Decode;
+use std::fmt::Debug;
+use ethereum_types::{U256, U128};
+use test_decode::TestDecode;
+
+mod error;
+mod test_decode;
 
 #[derive(Debug, Deserialize)]
 pub struct TestDoc<T> {
@@ -21,6 +29,66 @@ pub struct SszGenericCase {
     pub ssz: Option<String>,
 }
 
+pub trait Test {
+    fn test(&self) -> Vec<Result<(), Error>>;
+}
+
+impl Test for TestDoc<SszGenericCase> {
+    fn test(&self) -> Vec<Result<(), Error>> {
+        self
+            .test_cases
+            .iter()
+            .map(|tc| {
+                if let Some(ssz) = &tc.ssz {
+                    match tc.type_name.as_ref() {
+                        "uint8" => compare_decoding::<u8>(tc.valid, ssz, &tc.value),
+                        "uint16" => compare_decoding::<u16>(tc.valid, ssz, &tc.value),
+                        "uint32" => compare_decoding::<u32>(tc.valid, ssz, &tc.value),
+                        "uint64" => compare_decoding::<u64>(tc.valid, ssz, &tc.value),
+                        "uint128" => compare_decoding::<U128>(tc.valid, ssz, &tc.value),
+                        "uint256" => compare_decoding::<U256>(tc.valid, ssz, &tc.value),
+                        _ => {
+                            Err(Error::FailedToParseTest(format!("Unknown type: {}", tc.type_name)))
+                        }
+                    }
+                } else {
+                    // Skip tests that do not have an ssz field.
+                    //
+                    // See: https://github.com/ethereum/eth2.0-specs/issues/1079
+                    Ok(())
+                }
+            })
+            .collect()
+    }
+}
+
+fn compare_decoding<T>(should_pass: bool, ssz: &String, value: &String) -> Result<(), Error>
+where
+    T: Decode + TestDecode + Debug + PartialEq<T>,
+{
+    let ssz = hex::decode(&ssz[2..])
+        .map_err(|e| Error::FailedToParseTest(format!("{:?}", e)))?;
+    let expected = T::test_decode(value)?;
+
+    let decoded = T::from_ssz_bytes(&ssz);
+
+    if should_pass {
+        let decoded = decoded.map_err(|e| Error::NotEqual(format!("{:?}", e)))?;
+
+        if decoded != expected {
+            Err(Error::NotEqual(format!("{:?} != {:?}", decoded, expected)))
+        } else {
+            Ok(())
+        }
+    } else {
+        if let Ok(decoded) = decoded {
+            Err(Error::DidntFail(format!("Decoded as {:?}", decoded)))
+        } else {
+            Ok(())
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     #[test]
diff --git a/tests/ef_tests/src/test_decode.rs b/tests/ef_tests/src/test_decode.rs
new file mode 100644
index 000000000..dbbbcdae0
--- /dev/null
+++ b/tests/ef_tests/src/test_decode.rs
@@ -0,0 +1,35 @@
+use super::*;
+
+pub trait TestDecode: Sized {
+    fn test_decode(string: &String) -> Result<Self, Error>;
+}
+
+macro_rules! impl_via_parse {
+    ($ty: ty) => {
+        impl TestDecode for $ty {
+            fn test_decode(string: &String) -> Result<Self, Error> {
+                string
+                    .parse::<Self>()
+                    .map_err(|e| Error::FailedToParseTest(format!("{:?}", e)))
+            }
+        }
+    };
+}
+
+impl_via_parse!(u8);
+impl_via_parse!(u16);
+impl_via_parse!(u32);
+impl_via_parse!(u64);
+
+macro_rules! impl_via_from_dec_str {
+    ($ty: ty) => {
+        impl TestDecode for $ty {
+            fn test_decode(string: &String) -> Result<Self, Error> {
+                Self::from_dec_str(string).map_err(|e| Error::FailedToParseTest(format!("{:?}", e)))
+            }
+        }
+    };
+}
+
+impl_via_from_dec_str!(U128);
+impl_via_from_dec_str!(U256);
diff --git a/tests/ef_tests/tests/tests.rs b/tests/ef_tests/tests/tests.rs
index 023b7c18a..46fa4e9cb 100644
--- a/tests/ef_tests/tests/tests.rs
+++ b/tests/ef_tests/tests/tests.rs
@@ -21,7 +21,15 @@ fn load_test_case<T: DeserializeOwned>(test_name: &str) -> TestDoc<T> {
 fn ssz() {
     let doc: TestDoc<SszGenericCase> = load_test_case("ssz_generic/uint/uint_bounds.yaml");
 
-    dbg!(doc);
+    let results = doc.test();
 
-    assert!(false);
+    let failures: Vec<(usize, &Result<_, _>)> = results
+        .iter()
+        .enumerate()
+        .filter(|(_i, r)| r.is_ok())
+        .collect();
+
+    if !failures.is_empty() {
+        panic!("{:?}", failures);
+    }
 }