diff --git a/lib/memory/leak/cluster.rb b/lib/memory/leak/cluster.rb
index 31d0992..ef85835 100644
--- a/lib/memory/leak/cluster.rb
+++ b/lib/memory/leak/cluster.rb
@@ -87,7 +87,7 @@ def apply_limit!(total_size_limit = @total_size_limit)
 			def sample!
 				System.memory_usages(@processes.keys) do |process_id, memory_usage|
 					if monitor = @processes[process_id]
-						monitor.current_size = memory_usage
+						monitor.sample!(memory_usage)
 					end
 				end
 			end
@@ -96,8 +96,6 @@ def sample!
 			#
 			# @yields {|process_id, monitor| ...} each process ID and monitor that is leaking or exceeds the memory limit.
 			def check!(&block)
-				return to_enum(__method__) unless block_given?
-				
 				self.sample!
 				
 				leaking = []
@@ -110,10 +108,14 @@ def check!(&block)
 					end
 				end
 				
-				leaking.each(&block)
+				if block_given?
+					leaking.each(&block)
+				end
 				
 				# Finally, apply any per-cluster memory limits:
 				apply_limit!(@total_size_limit, &block) if @total_size_limit
+				
+				return leaking
 			end
 		end
 	end
diff --git a/lib/memory/leak/monitor.rb b/lib/memory/leak/monitor.rb
index 5686070..cb7d988 100644
--- a/lib/memory/leak/monitor.rb
+++ b/lib/memory/leak/monitor.rb
@@ -33,9 +33,11 @@ class Monitor
 			def initialize(process_id = Process.pid, maximum_size: nil, maximum_size_limit: nil, threshold_size: DEFAULT_THRESHOLD_SIZE, increase_limit: DEFAULT_INCREASE_LIMIT)
 				@process_id = process_id
 				
+				@sample_count = 0
 				@current_size = nil
 				@maximum_size = maximum_size
 				@maximum_size_limit = maximum_size_limit
+				@maximum_observed_size = nil
 				
 				@threshold_size = threshold_size
 				@increase_count = 0
@@ -46,6 +48,7 @@ def initialize(process_id = Process.pid, maximum_size: nil, maximum_size_limit:
 			def as_json(...)
 				{
 					process_id: @process_id,
+					sample_count: @sample_count,
 					current_size: @current_size,
 					maximum_size: @maximum_size,
 					maximum_size_limit: @maximum_size_limit,
@@ -83,6 +86,9 @@ def memory_usage
 				System.memory_usage(@process_id)
 			end
 			
+			# @attribute [Integer] The number of samples taken.
+			attr :sample_count
+			
 			# @returns [Integer] The last sampled memory usage.
 			def current_size
 				@current_size ||= memory_usage
@@ -119,7 +125,9 @@ def leaking?
 			# Capture a memory usage sample and yield if a memory leak is detected.
 			#
 			# @yields {|sample, monitor| ...} If a memory leak is detected.
-			def sample!
+			def sample!(memory_usage = self.memory_usage)
+				@sample_count += 1
+				
 				self.current_size = memory_usage
 				
 				if @maximum_observed_size
diff --git a/releases.md b/releases.md
index e322a82..e8a8e7f 100644
--- a/releases.md
+++ b/releases.md
@@ -1,5 +1,11 @@
 # Releases
 
+## Unreleased
+
+  - Added `sample_count` attribute to monitor to track number of samples taken.
+  - `check!` method in cluster now returns an array of leaking monitors if no block is given.
+  - `Cluster#check!` now invokes `Monitor#sample!` to ensure memory usage is updated before checking for leaks.
+
 ## v0.5.0
 
   - Improved variable names.
diff --git a/test/memory/leak/cluster.rb b/test/memory/leak/cluster.rb
index e8a867b..0cf52a3 100644
--- a/test/memory/leak/cluster.rb
+++ b/test/memory/leak/cluster.rb
@@ -45,6 +45,18 @@
 		
 		attr :children
 		
+		it "samples memory usage" do
+			cluster.check!.to_a
+			
+			children.each do |process_id, child|
+				monitor = cluster.processes[process_id]
+				expect(monitor).to have_attributes(
+					sample_count: be > 0,
+					current_size: be_a(Integer),
+				)
+			end
+		end
+		
 		it "can detect memory leaks" do
 			child = children.values.first
 			monitor = cluster.processes[child.process_id]
@@ -58,6 +70,10 @@
 				monitor.sample!
 			end
 			
+			expect(monitor).to have_attributes(
+				sample_count: be > 0,
+			)
+			
 			cluster.check! do |process_id, monitor|
 				expect(process_id).to be == child.process_id
 				expect(monitor.increase_count).to be == monitor.increase_limit
diff --git a/test/memory/leak/monitor.rb b/test/memory/leak/monitor.rb
index 791e764..9d3771d 100644
--- a/test/memory/leak/monitor.rb
+++ b/test/memory/leak/monitor.rb
@@ -36,6 +36,7 @@
 			# It is very unlikely that in the above test, the threshold of the 2nd and 3rd samples will be greater than the threshold of the 1st sample.
 			# Therefore, the count should be 0.
 			expect(monitor.increase_count).to be == 0
+			expect(monitor.sample_count).to be == 3
 		end
 		
 		with "a leaking child process" do