diff --git a/beacon_node/rpc/src/beacon_block.rs b/beacon_node/rpc/src/beacon_block.rs
index 6317414b0..29a61766e 100644
--- a/beacon_node/rpc/src/beacon_block.rs
+++ b/beacon_node/rpc/src/beacon_block.rs
@@ -1,3 +1,4 @@
+use crate::beacon_chain::BeaconChain;
 use crossbeam_channel;
 use eth2_libp2p::rpc::methods::BlockRootSlot;
 use eth2_libp2p::PubsubMessage;
@@ -9,13 +10,15 @@ use protos::services::{
     PublishBeaconBlockRequest, PublishBeaconBlockResponse,
 };
 use protos::services_grpc::BeaconBlockService;
-use slog::debug;
 use slog::Logger;
+use slog::{debug, error, info, warn};
 use ssz::{Decodable, TreeHash};
+use std::sync::Arc;
 use types::{BeaconBlock, Hash256, Slot};
 
 #[derive(Clone)]
 pub struct BeaconBlockServiceInstance {
+    pub chain: Arc<BeaconChain>,
     pub network_chan: crossbeam_channel::Sender<NetworkMessage>,
     pub log: Logger,
 }
@@ -50,39 +53,91 @@ impl BeaconBlockService for BeaconBlockServiceInstance {
         req: PublishBeaconBlockRequest,
         sink: UnarySink<PublishBeaconBlockResponse>,
     ) {
-        debug!(self.log, "PublishBeaconBlock");
+        let mut resp = PublishBeaconBlockResponse::new();
 
-        let block = req.get_block();
+        let ssz_serialized_block = req.get_block().get_ssz();
 
-        match BeaconBlock::ssz_decode(block.get_ssz(), 0) {
+        match BeaconBlock::ssz_decode(ssz_serialized_block, 0) {
             Ok((block, _i)) => {
                 let block_root = Hash256::from_slice(&block.hash_tree_root()[..]);
 
-                // TODO: Obtain topics from the network service properly.
-                let topic = types::TopicBuilder::new("beacon_chain".to_string()).build();
-                let message = PubsubMessage::Block(BlockRootSlot {
-                    block_root,
-                    slot: block.slot,
-                });
+                match self.chain.process_block(block.clone()) {
+                    Ok(outcome) => {
+                        if outcome.sucessfully_processed() {
+                            // Block was successfully processed.
+                            info!(
+                                self.log,
+                                "PublishBeaconBlock";
+                                "type" => "invalid_block",
+                                "outcome" => format!("{:?}", outcome)
+                            );
 
-                println!("Sending beacon block to gossipsub");
-                self.network_chan.send(NetworkMessage::Publish {
-                    topics: vec![topic],
-                    message,
-                });
+                            // TODO: Obtain topics from the network service properly.
+                            let topic =
+                                types::TopicBuilder::new("beacon_chain".to_string()).build();
+                            let message = PubsubMessage::Block(BlockRootSlot {
+                                block_root,
+                                slot: block.slot,
+                            });
+
+                            println!("Sending beacon block to gossipsub");
+                            self.network_chan.send(NetworkMessage::Publish {
+                                topics: vec![topic],
+                                message,
+                            });
+
+                            resp.set_success(true);
+                        } else if outcome.is_invalid() {
+                            // Block was invalid.
+                            warn!(
+                                self.log,
+                                "PublishBeaconBlock";
+                                "type" => "invalid_block",
+                                "outcome" => format!("{:?}", outcome)
+                            );
+
+                            resp.set_success(false);
+                            resp.set_msg(
+                                format!("InvalidBlock: {:?}", outcome).as_bytes().to_vec(),
+                            );
+                        } else {
+                            // Some failure during processing.
+                            error!(
+                                self.log,
+                                "PublishBeaconBlock";
+                                "type" => "other",
+                                "outcome" => format!("{:?}", outcome)
+                            );
+
+                            resp.set_success(false);
+                            resp.set_msg(format!("other: {:?}", outcome).as_bytes().to_vec());
+                        }
+                    }
+                    Err(e) => {
+                        // Some failure during processing.
+                        error!(
+                            self.log,
+                            "PublishBeaconBlock";
+                            "type" => "failed_to_process",
+                            "error" => format!("{:?}", e)
+                        );
+
+                        resp.set_success(false);
+                        resp.set_msg(format!("failed_to_process: {:?}", e).as_bytes().to_vec());
+                    }
+                }
 
-                // TODO: actually process the block.
-                let mut resp = PublishBeaconBlockResponse::new();
                 resp.set_success(true);
+            }
+            Err(_) => {
+                resp.set_success(false);
+                resp.set_msg(b"Invalid SSZ".to_vec());
+            }
+        };
 
-                let f = sink
-                    .success(resp)
-                    .map_err(move |e| println!("failed to reply {:?}: {:?}", req, e));
-                ctx.spawn(f)
-            }
-            Err(e) => {
-                //
-            }
-        }
+        let f = sink
+            .success(resp)
+            .map_err(move |e| println!("failed to reply {:?}: {:?}", req, e));
+        ctx.spawn(f)
     }
 }
diff --git a/beacon_node/rpc/src/beacon_chain.rs b/beacon_node/rpc/src/beacon_chain.rs
index 9b2681876..0551a8024 100644
--- a/beacon_node/rpc/src/beacon_chain.rs
+++ b/beacon_node/rpc/src/beacon_chain.rs
@@ -5,14 +5,18 @@ use beacon_chain::{
     parking_lot::RwLockReadGuard,
     slot_clock::SlotClock,
     types::{BeaconState, ChainSpec},
-    CheckPoint,
 };
+pub use beacon_chain::{BeaconChainError, BlockProcessingOutcome};
+use types::BeaconBlock;
 
 /// The RPC's API to the beacon chain.
 pub trait BeaconChain: Send + Sync {
     fn get_spec(&self) -> &ChainSpec;
 
     fn get_state(&self) -> RwLockReadGuard<BeaconState>;
+
+    fn process_block(&self, block: BeaconBlock)
+        -> Result<BlockProcessingOutcome, BeaconChainError>;
 }
 
 impl<T, U, F> BeaconChain for RawBeaconChain<T, U, F>
@@ -28,4 +32,11 @@ where
     fn get_state(&self) -> RwLockReadGuard<BeaconState> {
         self.state.read()
     }
+
+    fn process_block(
+        &self,
+        block: BeaconBlock,
+    ) -> Result<BlockProcessingOutcome, BeaconChainError> {
+        self.process_block(block)
+    }
 }
diff --git a/beacon_node/rpc/src/lib.rs b/beacon_node/rpc/src/lib.rs
index 4dfd33487..289a81f3a 100644
--- a/beacon_node/rpc/src/lib.rs
+++ b/beacon_node/rpc/src/lib.rs
@@ -43,6 +43,7 @@ pub fn start_server(
 
     let beacon_block_service = {
         let instance = BeaconBlockServiceInstance {
+            chain: beacon_chain.clone(),
             network_chan,
             log: log.clone(),
         };