diff --git a/Cargo.toml b/Cargo.toml
index 835d37edc4..7e46412981 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -36,7 +36,6 @@ members = [
 	"beacon_chain/chain",
 	"beacon_chain/naive_fork_choice",
 	"beacon_chain/spec",
-	"beacon_chain/state-transition",
 	"beacon_chain/types",
 	"beacon_chain/utils/bls",
 	"beacon_chain/utils/boolean-bitfield",
diff --git a/beacon_chain/chain/Cargo.toml b/beacon_chain/chain/Cargo.toml
index aa0f48c625..4430dbe5b9 100644
--- a/beacon_chain/chain/Cargo.toml
+++ b/beacon_chain/chain/Cargo.toml
@@ -8,7 +8,6 @@ bls = { path = "../utils/bls" }
 db = { path = "../../lighthouse/db" }
 naive_fork_choice = { path = "../naive_fork_choice" }
 ssz = { path = "../utils/ssz" }
-state-transition = { path = "../state-transition" }
 types = { path = "../types" }
 validator_induction = { path = "../validator_induction" }
 validator_shuffling = { path = "../validator_shuffling" }
diff --git a/beacon_chain/state-transition/Cargo.toml b/beacon_chain/state-transition/Cargo.toml
deleted file mode 100644
index 7beb8f6131..0000000000
--- a/beacon_chain/state-transition/Cargo.toml
+++ /dev/null
@@ -1,7 +0,0 @@
-[package]
-name = "state-transition"
-version = "0.1.0"
-authors = ["Paul Hauner <paul@paulhauner.com>"]
-
-[dependencies]
-types = { path = "../types" }
diff --git a/beacon_chain/state-transition/src/lib.rs b/beacon_chain/state-transition/src/lib.rs
deleted file mode 100644
index ee8d841e60..0000000000
--- a/beacon_chain/state-transition/src/lib.rs
+++ /dev/null
@@ -1,194 +0,0 @@
-extern crate types;
-
-use types::{ActiveState, BeaconBlock, Hash256};
-
-#[derive(Debug, PartialEq)]
-pub enum StateTransitionError {
-    BlockSlotBeforeRecalcSlot,
-    InvalidParentHashes,
-    DBError(String),
-}
-
-pub fn extend_active_state(
-    act_state: &ActiveState,
-    block: &BeaconBlock,
-    block_hash: &Hash256,
-) -> Result<ActiveState, StateTransitionError> {
-    /*
-     * Extend the pending attestations in the active state with the new attestations included
-     * in the block.
-     *
-     * Using the concat method to avoid reallocations.
-     */
-    let pending_attestations =
-        [&act_state.pending_attestations[..], &block.attestations[..]].concat();
-
-    /*
-     * Extend the pending specials in the active state with the new specials included in the
-     * block.
-     *
-     * Using the concat method to avoid reallocations.
-     */
-    let pending_specials = [&act_state.pending_specials[..], &block.specials[..]].concat();
-
-    /*
-     * Update the active state recent_block_hashes:
-     *
-     * - Drop the hash from the earliest position.
-     * - Push the block_hash into the latest position.
-     *
-     * Using the concat method to avoid reallocations.
-     */
-    let (_first_hash, last_hashes) = act_state
-        .recent_block_hashes
-        .split_first()
-        .ok_or(StateTransitionError::InvalidParentHashes)?;
-    let new_hash = &[block_hash.clone()];
-    let recent_block_hashes = [&last_hashes, &new_hash[..]].concat();
-
-    /*
-     * The new `randao_mix` is set to the XOR of the previous active state randao mix and the
-     * randao reveal in this block.
-     */
-    let randao_mix = act_state.randao_mix ^ block.randao_reveal;
-
-    Ok(ActiveState {
-        pending_attestations,
-        pending_specials,
-        recent_block_hashes,
-        randao_mix,
-    })
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-    use types::SpecialRecord;
-
-    fn empty_active_state() -> ActiveState {
-        ActiveState {
-            pending_attestations: vec![],
-            pending_specials: vec![],
-            recent_block_hashes: vec![],
-            randao_mix: Hash256::zero(),
-        }
-    }
-
-    #[test]
-    fn test_extend_active_state_minimal() {
-        let mut act_state = empty_active_state();
-
-        let parent_hash = Hash256::from("parent_hash".as_bytes());
-        act_state.recent_block_hashes = vec![parent_hash];
-
-        let block = BeaconBlock::zero();
-        let block_hash = Hash256::from("block_hash".as_bytes());
-
-        let new_act_state = extend_active_state(&act_state, &block, &block_hash).unwrap();
-
-        assert_eq!(new_act_state.pending_attestations, vec![]);
-        assert_eq!(new_act_state.pending_specials, vec![]);
-        assert_eq!(new_act_state.recent_block_hashes, vec![block_hash]);
-        assert_eq!(new_act_state.randao_mix, Hash256::zero());
-    }
-
-    #[test]
-    fn test_extend_active_state_specials() {
-        let mut act_state = empty_active_state();
-
-        let parent_hash = Hash256::from("parent_hash".as_bytes());
-        act_state.recent_block_hashes = vec![parent_hash];
-
-        let mut block = BeaconBlock::zero();
-        let special = SpecialRecord {
-            kind: 0,
-            data: vec![42, 42],
-        };
-
-        block.specials.push(special.clone());
-
-        let block_hash = Hash256::from("block_hash".as_bytes());
-
-        let new_act_state = extend_active_state(&act_state, &block, &block_hash).unwrap();
-
-        assert_eq!(new_act_state.pending_attestations, vec![]);
-        assert_eq!(new_act_state.pending_specials, vec![special.clone()]);
-        assert_eq!(new_act_state.recent_block_hashes, vec![block_hash]);
-        assert_eq!(new_act_state.randao_mix, Hash256::zero());
-
-        let new_new_act_state = extend_active_state(&new_act_state, &block, &block_hash).unwrap();
-
-        assert_eq!(new_new_act_state.pending_attestations, vec![]);
-        assert_eq!(
-            new_new_act_state.pending_specials,
-            vec![special.clone(), special.clone()]
-        );
-        assert_eq!(new_new_act_state.recent_block_hashes, vec![block_hash]);
-        assert_eq!(new_new_act_state.randao_mix, Hash256::zero());
-    }
-
-    #[test]
-    fn test_extend_active_state_empty_recent_block_hashes() {
-        let act_state = empty_active_state();
-
-        let block = BeaconBlock::zero();
-
-        let block_hash = Hash256::from("block_hash".as_bytes());
-
-        let result = extend_active_state(&act_state, &block, &block_hash);
-
-        assert_eq!(result, Err(StateTransitionError::InvalidParentHashes));
-    }
-
-    #[test]
-    fn test_extend_active_recent_block_hashes() {
-        let mut act_state = empty_active_state();
-
-        let parent_hashes = vec![
-            Hash256::from("one".as_bytes()),
-            Hash256::from("two".as_bytes()),
-            Hash256::from("three".as_bytes()),
-        ];
-        act_state.recent_block_hashes = parent_hashes.clone();
-
-        let block = BeaconBlock::zero();
-
-        let block_hash = Hash256::from("four".as_bytes());
-
-        let new_act_state = extend_active_state(&act_state, &block, &block_hash).unwrap();
-
-        assert_eq!(new_act_state.pending_attestations, vec![]);
-        assert_eq!(new_act_state.pending_specials, vec![]);
-        assert_eq!(
-            new_act_state.recent_block_hashes,
-            vec![
-                Hash256::from("two".as_bytes()),
-                Hash256::from("three".as_bytes()),
-                Hash256::from("four".as_bytes()),
-            ]
-        );
-        assert_eq!(new_act_state.randao_mix, Hash256::zero());
-    }
-
-    #[test]
-    fn test_extend_active_state_randao() {
-        let mut act_state = empty_active_state();
-
-        let parent_hash = Hash256::from("parent_hash".as_bytes());
-        act_state.recent_block_hashes = vec![parent_hash];
-
-        act_state.randao_mix = Hash256::from(0b00000000);
-
-        let mut block = BeaconBlock::zero();
-        block.randao_reveal = Hash256::from(0b00000001);
-
-        let block_hash = Hash256::from("block_hash".as_bytes());
-
-        let new_act_state = extend_active_state(&act_state, &block, &block_hash).unwrap();
-
-        assert_eq!(new_act_state.pending_attestations, vec![]);
-        assert_eq!(new_act_state.pending_specials, vec![]);
-        assert_eq!(new_act_state.recent_block_hashes, vec![block_hash]);
-        assert_eq!(new_act_state.randao_mix, Hash256::from(0b00000001));
-    }
-}