diff --git a/include/bitcoin/node/chasers/chaser_candidate.hpp b/include/bitcoin/node/chasers/chaser_candidate.hpp
index bd7c809f..3e857e49 100644
--- a/include/bitcoin/node/chasers/chaser_candidate.hpp
+++ b/include/bitcoin/node/chasers/chaser_candidate.hpp
@@ -29,7 +29,6 @@ namespace node {
 class full_node;
 
 /// Construct candidate blocks upon modification of the transaction DAG.
-/// Notify subscribers with "candidate" event.
 class BCN_API chaser_candidate
   : public chaser, protected network::tracker<chaser_candidate>
 {
@@ -37,6 +36,10 @@ class BCN_API chaser_candidate
     typedef std::unique_ptr<chaser_candidate> uptr;
 
     chaser_candidate(full_node& node) NOEXCEPT;
+
+private:
+    void handle_event(const code& ec, chase value) NOEXCEPT;
+    void do_handle_event(const code& ec, chase value) NOEXCEPT;
 };
 
 } // namespace node
diff --git a/include/bitcoin/node/chasers/chaser_check.hpp b/include/bitcoin/node/chasers/chaser_check.hpp
index 5dfcfc89..ac39fa28 100644
--- a/include/bitcoin/node/chasers/chaser_check.hpp
+++ b/include/bitcoin/node/chasers/chaser_check.hpp
@@ -29,7 +29,6 @@ namespace node {
 class full_node;
 
 /// Chase down blocks for the candidate header chain.
-/// Notify subscribers with "block checked" event.
 class BCN_API chaser_check
   : public chaser, protected network::tracker<chaser_check>
 {
diff --git a/include/bitcoin/node/chasers/chaser_confirm.hpp b/include/bitcoin/node/chasers/chaser_confirm.hpp
index 6eb0d77c..42d95e87 100644
--- a/include/bitcoin/node/chasers/chaser_confirm.hpp
+++ b/include/bitcoin/node/chasers/chaser_confirm.hpp
@@ -29,7 +29,6 @@ namespace node {
 class full_node;
 
 /// Chase down valid blocks for confirmation.
-/// Notify subscribers with "block confirmed" event.
 class BCN_API chaser_confirm
   : public chaser, protected network::tracker<chaser_confirm>
 {
@@ -37,6 +36,10 @@ class BCN_API chaser_confirm
     typedef std::unique_ptr<chaser_confirm> uptr;
 
     chaser_confirm(full_node& node) NOEXCEPT;
+
+private:
+    void handle_event(const code& ec, chase value) NOEXCEPT;
+    void do_handle_event(const code& ec, chase value) NOEXCEPT;
 };
 
 } // namespace node
diff --git a/include/bitcoin/node/chasers/chaser_connect.hpp b/include/bitcoin/node/chasers/chaser_connect.hpp
index 8b0dea8e..8297ad8e 100644
--- a/include/bitcoin/node/chasers/chaser_connect.hpp
+++ b/include/bitcoin/node/chasers/chaser_connect.hpp
@@ -29,7 +29,6 @@ namespace node {
 class full_node;
 
 /// Chase down blocks in the the candidate header chain for validation.
-/// Notify subscribers with the "block connected" event.
 class BCN_API chaser_connect
   : public chaser, protected network::tracker<chaser_connect>
 {
@@ -37,6 +36,10 @@ class BCN_API chaser_connect
     typedef std::unique_ptr<chaser_connect> uptr;
 
     chaser_connect(full_node& node) NOEXCEPT;
+
+private:
+    void handle_event(const code& ec, chase value) NOEXCEPT;
+    void do_handle_event(const code& ec, chase value) NOEXCEPT;
 };
 
 } // namespace node
diff --git a/include/bitcoin/node/chasers/chaser_header.hpp b/include/bitcoin/node/chasers/chaser_header.hpp
index 39bb6236..27b58d41 100644
--- a/include/bitcoin/node/chasers/chaser_header.hpp
+++ b/include/bitcoin/node/chasers/chaser_header.hpp
@@ -29,7 +29,6 @@ namespace node {
 class full_node;
 
 /// Chase down stronger header branches for the candidate chain.
-/// Notify subscribers with "strong header" event.
 class BCN_API chaser_header
   : public chaser, protected network::tracker<chaser_header>
 {
@@ -37,6 +36,10 @@ class BCN_API chaser_header
     typedef std::unique_ptr<chaser_header> uptr;
 
     chaser_header(full_node& node) NOEXCEPT;
+
+private:
+    void handle_event(const code& ec, chase value) NOEXCEPT;
+    void do_handle_event(const code& ec, chase value) NOEXCEPT;
 };
 
 } // namespace node
diff --git a/include/bitcoin/node/chasers/chaser_transaction.hpp b/include/bitcoin/node/chasers/chaser_transaction.hpp
index 20735ff1..31b49019 100644
--- a/include/bitcoin/node/chasers/chaser_transaction.hpp
+++ b/include/bitcoin/node/chasers/chaser_transaction.hpp
@@ -36,6 +36,10 @@ class BCN_API chaser_transaction
     typedef std::unique_ptr<chaser_transaction> uptr;
 
     chaser_transaction(full_node& node) NOEXCEPT;
+
+private:
+    void handle_event(const code& ec, chase value) NOEXCEPT;
+    void do_handle_event(const code& ec, chase value) NOEXCEPT;
 };
 
 } // namespace node
diff --git a/src/chasers/chaser_candidate.cpp b/src/chasers/chaser_candidate.cpp
index 589abe4d..bef2ea71 100644
--- a/src/chasers/chaser_candidate.cpp
+++ b/src/chasers/chaser_candidate.cpp
@@ -18,19 +18,51 @@
  */
 #include <bitcoin/node/chasers/chaser_candidate.hpp>
 
+#include <functional>
 #include <bitcoin/network.hpp>
+#include <bitcoin/node/error.hpp>
 #include <bitcoin/node/full_node.hpp>
 #include <bitcoin/node/chasers/chaser.hpp>
 
 namespace libbitcoin {
 namespace node {
 
+using namespace std::placeholders;
+
 BC_PUSH_WARNING(NO_THROW_IN_NOEXCEPT)
 
 chaser_candidate::chaser_candidate(full_node& node) NOEXCEPT
   : chaser(node),
     tracker<chaser_candidate>(node.log)
 {
+    subscribe(std::bind(&chaser_candidate::handle_event, this, _1, _2));
+}
+
+void chaser_candidate::handle_event(const code& ec, chase value) NOEXCEPT
+{
+    boost::asio::post(strand(),
+        std::bind(&chaser_candidate::do_handle_event, this, ec, value));
+}
+
+void chaser_candidate::do_handle_event(const code& ec, chase value) NOEXCEPT
+{
+    BC_ASSERT_MSG(stranded(), "chaser_candidate");
+
+    // The code should be error::service_stopped when error::stop is set.
+    if (ec)
+        return;
+
+    switch (value)
+    {
+        case chase::start:
+            // TODO: initialize.
+            break;
+        case chase::transaction:
+            // TODO: handle transaction graph change (may issue 'candidate').
+            break;
+        default:
+            return;
+    }
 }
 
 BC_POP_WARNING()
diff --git a/src/chasers/chaser_confirm.cpp b/src/chasers/chaser_confirm.cpp
index 7ab99e2a..fc543e46 100644
--- a/src/chasers/chaser_confirm.cpp
+++ b/src/chasers/chaser_confirm.cpp
@@ -18,19 +18,51 @@
  */
 #include <bitcoin/node/chasers/chaser_confirm.hpp>
 
+#include <functional>
 #include <bitcoin/network.hpp>
+#include <bitcoin/node/error.hpp>
 #include <bitcoin/node/full_node.hpp>
 #include <bitcoin/node/chasers/chaser.hpp>
 
 namespace libbitcoin {
 namespace node {
 
+using namespace std::placeholders;
+
 BC_PUSH_WARNING(NO_THROW_IN_NOEXCEPT)
 
 chaser_confirm::chaser_confirm(full_node& node) NOEXCEPT
   : chaser(node),
     tracker<chaser_confirm>(node.log)
 {
+    subscribe(std::bind(&chaser_confirm::handle_event, this, _1, _2));
+}
+
+void chaser_confirm::handle_event(const code& ec, chase value) NOEXCEPT
+{
+    boost::asio::post(strand(),
+        std::bind(&chaser_confirm::do_handle_event, this, ec, value));
+}
+
+void chaser_confirm::do_handle_event(const code& ec, chase value) NOEXCEPT
+{
+    BC_ASSERT_MSG(stranded(), "chaser_confirm");
+
+    // The code should be error::service_stopped when error::stop is set.
+    if (ec)
+        return;
+
+    switch (value)
+    {
+        case chase::start:
+            // TODO: initialize.
+            break;
+        case chase::connected:
+            // TODO: handle new strong connected branch (may issue 'confirmed').
+            break;
+        default:
+            return;
+    }
 }
 
 BC_POP_WARNING()
diff --git a/src/chasers/chaser_connect.cpp b/src/chasers/chaser_connect.cpp
index f850b1ec..c3d7c5e4 100644
--- a/src/chasers/chaser_connect.cpp
+++ b/src/chasers/chaser_connect.cpp
@@ -18,19 +18,51 @@
  */
 #include <bitcoin/node/chasers/chaser_connect.hpp>
 
+#include <functional>
 #include <bitcoin/network.hpp>
+#include <bitcoin/node/error.hpp>
 #include <bitcoin/node/full_node.hpp>
 #include <bitcoin/node/chasers/chaser.hpp>
 
 namespace libbitcoin {
 namespace node {
 
+using namespace std::placeholders;
+
 BC_PUSH_WARNING(NO_THROW_IN_NOEXCEPT)
 
 chaser_connect::chaser_connect(full_node& node) NOEXCEPT
   : chaser(node),
     tracker<chaser_connect>(node.log)
 {
+    subscribe(std::bind(&chaser_connect::handle_event, this, _1, _2));
+}
+
+void chaser_connect::handle_event(const code& ec, chase value) NOEXCEPT
+{
+    boost::asio::post(strand(),
+        std::bind(&chaser_connect::do_handle_event, this, ec, value));
+}
+
+void chaser_connect::do_handle_event(const code& ec, chase value) NOEXCEPT
+{
+    BC_ASSERT_MSG(stranded(), "chaser_connect");
+
+    // The code should be error::service_stopped when error::stop is set.
+    if (ec)
+        return;
+
+    switch (value)
+    {
+        case chase::start:
+            // TODO: initialize.
+            break;
+        case chase::checked:
+            // TODO: handle the new checked blocks (may issue 'connected').
+            break;
+        default:
+            return;
+    }
 }
 
 BC_POP_WARNING()
diff --git a/src/chasers/chaser_header.cpp b/src/chasers/chaser_header.cpp
index 4b898ef4..b02efe61 100644
--- a/src/chasers/chaser_header.cpp
+++ b/src/chasers/chaser_header.cpp
@@ -18,21 +18,52 @@
  */
 #include <bitcoin/node/chasers/chaser_header.hpp>
 
+#include <functional>
 #include <bitcoin/network.hpp>
+#include <bitcoin/node/error.hpp>
 #include <bitcoin/node/full_node.hpp>
 #include <bitcoin/node/chasers/chaser.hpp>
 
 namespace libbitcoin {
 namespace node {
 
+using namespace std::placeholders;
+
 BC_PUSH_WARNING(NO_THROW_IN_NOEXCEPT)
 
 chaser_header::chaser_header(full_node& node) NOEXCEPT
   : chaser(node),
     tracker<chaser_header>(node.log)
 {
+    subscribe(std::bind(&chaser_header::handle_event, this, _1, _2));
+}
+
+void chaser_header::handle_event(const code& ec, chase value) NOEXCEPT
+{
+    boost::asio::post(strand(),
+        std::bind(&chaser_header::do_handle_event, this, ec, value));
+}
+
+void chaser_header::do_handle_event(const code& ec, chase value) NOEXCEPT
+{
+    BC_ASSERT_MSG(stranded(), "chaser_header");
+
+    // The code should be error::service_stopped when error::stop is set.
+    if (ec)
+        return;
+
+    switch (value)
+    {
+        case chase::start:
+            // TODO: initialize.
+            break;
+        default:
+            return;
+    }
 }
 
+// TODO: handle new headers (may issue 'header').
+
 BC_POP_WARNING()
 
 } // namespace database
diff --git a/src/chasers/chaser_transaction.cpp b/src/chasers/chaser_transaction.cpp
index ed3d4328..8f6c2de7 100644
--- a/src/chasers/chaser_transaction.cpp
+++ b/src/chasers/chaser_transaction.cpp
@@ -18,21 +18,55 @@
  */
 #include <bitcoin/node/chasers/chaser_transaction.hpp>
 
+#include <functional>
 #include <bitcoin/network.hpp>
+#include <bitcoin/node/error.hpp>
 #include <bitcoin/node/full_node.hpp>
 #include <bitcoin/node/chasers/chaser.hpp>
 
 namespace libbitcoin {
 namespace node {
 
+using namespace std::placeholders;
+
 BC_PUSH_WARNING(NO_THROW_IN_NOEXCEPT)
 
 chaser_transaction::chaser_transaction(full_node& node) NOEXCEPT
   : chaser(node),
     tracker<chaser_transaction>(node.log)
 {
+    subscribe(std::bind(&chaser_transaction::handle_event, this, _1, _2));
+}
+
+void chaser_transaction::handle_event(const code& ec, chase value) NOEXCEPT
+{
+    boost::asio::post(strand(),
+        std::bind(&chaser_transaction::do_handle_event, this, ec, value));
+}
+
+void chaser_transaction::do_handle_event(const code& ec, chase value) NOEXCEPT
+{
+    BC_ASSERT_MSG(stranded(), "chaser_transaction");
+
+    // The code should be error::service_stopped when error::stop is set.
+    if (ec)
+        return;
+
+    switch (value)
+    {
+        case chase::start:
+            // TODO: initialize.
+            break;
+        case chase::confirmed:
+            // TODO: handle the new confirmed blocks (may issue 'transaction').
+            break;
+        default:
+            return;
+    }
 }
 
+// TODO: handle the new unconfirmed transactions (may issue 'transaction').
+
 BC_POP_WARNING()
 
 } // namespace database