diff --git a/lib/aws-missing-tools/aws-ha-release/aws-ha-release.rb b/lib/aws-missing-tools/aws-ha-release/aws-ha-release.rb
index b612984..a436dbf 100755
--- a/lib/aws-missing-tools/aws-ha-release/aws-ha-release.rb
+++ b/lib/aws-missing-tools/aws-ha-release/aws-ha-release.rb
@@ -21,6 +21,8 @@ module AwsMissingTools
         raise ArgumentError, "The Auto Scaling Group named #{@opts[:as_group_name]} does not exist in #{@opts[:region]}."
       end
 
+      @opts[:num_simultaneous_instances] = Integer(@opts[:num_simultaneous_instances]) rescue @group.auto_scaling_instances.count
+
       @max_size_change = 0
       @time_spent_inservice = 0
     end
@@ -64,7 +66,7 @@ module AwsMissingTools
         end
 
         opts.on('-n', '--num-simultaneous-instances NUM', 'Number of instances to simultaneously bring up per iteration') do |v|
-          options[:num_simultaneous_instances] = v.to_i
+          options[:num_simultaneous_instances] = v
         end
       end.parse!(arguments)
 
@@ -98,6 +100,7 @@ module AwsMissingTools
       @group.update(desired_capacity: @group.desired_capacity + @opts[:num_simultaneous_instances])
 
       puts "The list of instances in Auto Scaling Group #{@group.name} that will be terminated is:\n#{@group.auto_scaling_instances.map{ |i| i.ec2_instance.id }.to_ary}"
+      puts "The number of instances that will be brought up simultaneously is: #{@opts[:num_simultaneous_instances]}"
       @group.auto_scaling_instances.to_a.each_slice(@opts[:num_simultaneous_instances]) do |instances|
         time_taken = 0
 
diff --git a/spec/aws-missing-tools/aws-ha-release/aws-ha-release_spec.rb b/spec/aws-missing-tools/aws-ha-release/aws-ha-release_spec.rb
index 04736b5..94e1be1 100644
--- a/spec/aws-missing-tools/aws-ha-release/aws-ha-release_spec.rb
+++ b/spec/aws-missing-tools/aws-ha-release/aws-ha-release_spec.rb
@@ -28,6 +28,22 @@ describe 'aws-ha-release' do
         AwsMissingTools::AwsHaRelease.new(opts)
       }.should raise_error
     end
+
+    context 'number of simultaneous instances' do
+      before do
+        as.groups.create opts[1]
+        opts.push('--num-simultaneous-instances')
+      end
+      it 'with MAX, sets the option to the number of active instances' do
+        opts.push('MAX')
+        expect(AwsMissingTools::AwsHaRelease.new(opts).instance_variable_get('@opts')[:num_simultaneous_instances]).to eq 2
+      end
+
+      it 'with an integer, sets the option to that integer' do
+        opts.push('1')
+        expect(AwsMissingTools::AwsHaRelease.new(opts).instance_variable_get('@opts')[:num_simultaneous_instances]).to eq 1
+      end
+    end
   end
 
   describe '#parse_options' do
@@ -82,9 +98,17 @@ describe 'aws-ha-release' do
         end
       end
 
-      it 'number of instances to simultaneously bring up' do
-        [%w(-a test_group -n 2), %w(-a test_group --num-simultaneous-instances 2)].each do |options|
-          expect(AwsMissingTools::AwsHaRelease.parse_options(options)[:num_simultaneous_instances]).to eq 2
+      context 'number of instances to simultaneously bring up' do
+        it 'recognizes integer inputs' do
+          [%w(-a test_group -n 2), %w(-a test_group --num-simultaneous-instances 2)].each do |options|
+            expect(AwsMissingTools::AwsHaRelease.parse_options(options)[:num_simultaneous_instances]).to eq '2'
+          end
+        end
+
+        it 'recognizes the MAX keyword' do
+          [%w(-a test_group -n MAX), %w(-a test_group --num-simultaneous-instances MAX)].each do |options|
+            expect(AwsMissingTools::AwsHaRelease.parse_options(options)[:num_simultaneous_instances]).to eq 'MAX'
+          end
         end
       end
     end