Can anyone tell me if  it is possible to get binary data back from a web service callout?

I am using the apex Http, HttpRequest and HttpResponse classes to call an external  service that returns a binary file. I then attach that file to an email programatically. Everything works fine, except that my binary data in the attachment is mangled, because of the string conversion on response.getBody(). Is there a way to retrieve the binary stream from the HttpResponse class without corrupting it? 

Or is there another set of classes I should use to perform this function to get the results I'm looking for? 

Thanks for any help!

Gretchen