diff --git a/lib/hash_cast/casters/array_caster.rb b/lib/hash_cast/casters/array_caster.rb
index 6e1abf7..2a04381 100644
--- a/lib/hash_cast/casters/array_caster.rb
+++ b/lib/hash_cast/casters/array_caster.rb
@@ -1,14 +1,20 @@
 class HashCast::Casters::ArrayCaster
 
   def self.cast(value, attr_name, options = {})
-    if value.is_a?(Array)
-      if options[:each]
-        cast_array_items(value, attr_name, options)
-      else
-        value
+    unless value.is_a?(Array)
+      raise HashCast::Errors::CastingError, "should be an array"
+    end
+
+    if HashCast.config.array_size_validator_enabled
+      if value.size > HashCast.config.array_size_validator_limit
+        HashCast.config.array_size_validator_callback.call(value, attr_name, options)
       end
+    end
+
+    if options[:each]
+      cast_array_items(value, attr_name, options)
     else
-      raise HashCast::Errors::CastingError, "should be an array"
+      value
     end
   end
 
diff --git a/lib/hash_cast/casters/string_caster.rb b/lib/hash_cast/casters/string_caster.rb
index e40035c..675fb17 100644
--- a/lib/hash_cast/casters/string_caster.rb
+++ b/lib/hash_cast/casters/string_caster.rb
@@ -8,6 +8,12 @@ def self.cast(value, attr_name, options = {})
       raise HashCast::Errors::CastingError, 'contains invalid characters'
     end
 
+    if HashCast.config.string_size_validator_enabled
+      if value.size > HashCast.config.string_size_validator_limit
+        HashCast.config.string_size_validator_callback.call(value, attr_name, options)
+      end
+    end
+
     casted_value
   end
 
diff --git a/lib/hash_cast/config.rb b/lib/hash_cast/config.rb
index 5c0b874..2d858cc 100644
--- a/lib/hash_cast/config.rb
+++ b/lib/hash_cast/config.rb
@@ -1,5 +1,14 @@
 class HashCast::Config
-  attr_accessor :input_keys, :output_keys, :validate_string_null_byte
+  attr_writer :input_keys, :output_keys, :validate_string_null_byte, 
+    :array_size_validator_enabled, 
+    :array_size_validator_limit, 
+    :array_size_validator_callback,
+    :string_size_validator_enabled, 
+    :string_size_validator_limit, 
+    :string_size_validator_callback
+
+  DEFAULT_ARRAY_SIZE_VALIDATOR_LIMIT = 1000_000
+  DEFAULT_STRING_SIZE_VALIDATOR_LIMIT = 1000_000
 
   def input_keys
     @input_keys || :symbol
@@ -14,4 +23,48 @@ def validate_string_null_byte
     
     @validate_string_null_byte
   end
+
+  def array_size_validator_enabled
+    return false if @array_size_validator_enabled.nil?
+    
+    @array_size_validator_enabled
+  end
+
+  def array_size_validator_limit
+    return DEFAULT_ARRAY_SIZE_VALIDATOR_LIMIT if @array_size_validator_limit.nil?
+    
+    @array_size_validator_limit
+  end
+
+  def array_size_validator_callback
+    if @array_size_validator_callback.nil?
+      return lambda{ |value, name, options|
+        raise HashCast::Errors::CastingError, "array is too large" 
+      }
+    end
+    
+    @array_size_validator_callback
+  end
+
+  def string_size_validator_enabled
+    return false if @string_size_validator_enabled.nil?
+    
+    @string_size_validator_enabled
+  end
+
+  def string_size_validator_limit
+    return DEFAULT_STRING_SIZE_VALIDATOR_LIMIT if @string_size_validator_limit.nil?
+    
+    @string_size_validator_limit
+  end
+
+  def string_size_validator_callback
+    if @string_size_validator_callback.nil?
+      return lambda{ |value, name, options|
+        raise HashCast::Errors::CastingError, "string is too large" 
+      }
+    end
+    
+    @string_size_validator_callback
+  end
 end
diff --git a/spec/hash_cast/casters/array_caster_spec.rb b/spec/hash_cast/casters/array_caster_spec.rb
new file mode 100644
index 0000000..2c6d93d
--- /dev/null
+++ b/spec/hash_cast/casters/array_caster_spec.rb
@@ -0,0 +1,49 @@
+require 'spec_helper'
+
+describe HashCast::Casters::ArrayCaster do
+  subject { HashCast::Casters::ArrayCaster }
+
+  it "should cast an array" do
+    result = subject.cast([1,2,3], :ids)
+    expect(result).to eq([1,2,3])
+  end
+
+  it "should raise an error for non-array" do
+    expect {
+      subject.cast(1, :ids)
+    }.to raise_error(HashCast::Errors::CastingError, "should be an array")
+  end
+
+  context "array size validation" do
+    after{ 
+      HashCast.config.array_size_validator_enabled = nil
+      HashCast.config.array_size_validator_limit = nil
+    }
+
+    it "should not raise an error for large array by default" do
+      result = subject.cast([1] * 10_000, :ids)
+      expect(result).to eq([1] * 10_000)
+    end
+
+    it "should raise an error for large array when validation is enabled" do
+      HashCast.config.array_size_validator_enabled = true
+      HashCast.config.array_size_validator_limit = 1000
+
+      expect {
+        subject.cast([1] * 10_000, :ids)
+      }.to raise_error(HashCast::Errors::CastingError, "array is too large")
+    end
+
+    it "should allow overriding the callback" do
+      HashCast.config.array_size_validator_enabled = true
+      HashCast.config.array_size_validator_limit = 1000
+      HashCast.config.array_size_validator_callback = lambda { |value, name, options|
+        raise HashCast::Errors::UnexpectedAttributeError, 'test'
+      }
+
+      expect {
+        subject.cast([1] * 10_000, :ids)
+      }.to raise_error(HashCast::Errors::UnexpectedAttributeError, "test")
+    end
+  end
+end
diff --git a/spec/hash_cast/casters/string_caster_spec.rb b/spec/hash_cast/casters/string_caster_spec.rb
new file mode 100644
index 0000000..f54c54b
--- /dev/null
+++ b/spec/hash_cast/casters/string_caster_spec.rb
@@ -0,0 +1,43 @@
+require 'spec_helper'
+
+describe HashCast::Casters::StringCaster do
+  subject { HashCast::Casters::StringCaster }
+
+  it "should cast a string" do
+    result = subject.cast("foobar", :name)
+    expect(result).to eq("foobar")
+  end
+
+  context "string size validation" do
+    after{ 
+      HashCast.config.string_size_validator_enabled = nil
+      HashCast.config.string_size_validator_limit = nil
+    }
+
+    it "should not raise an error for large string by default" do
+      result = subject.cast("a" * 10_000, :name)
+      expect(result).to eq("a" * 10_000)
+    end
+
+    it "should raise an error for large string when validation is enabled" do
+      HashCast.config.string_size_validator_enabled = true
+      HashCast.config.string_size_validator_limit = 1000
+
+      expect {
+        subject.cast("a" * 10_000, :ids)
+      }.to raise_error(HashCast::Errors::CastingError, "string is too large")
+    end
+
+    it "should allow overriding the callback" do
+      HashCast.config.string_size_validator_enabled = true
+      HashCast.config.string_size_validator_limit = 1000
+      HashCast.config.string_size_validator_callback = lambda { |value, name, options|
+        raise HashCast::Errors::UnexpectedAttributeError, 'test'
+      }
+
+      expect {
+        subject.cast("a" * 10_000, :ids)
+      }.to raise_error(HashCast::Errors::UnexpectedAttributeError, "test")
+    end
+  end
+end