Since it took me quite some time to resolve this problem, I hope this post will be useful for someone else. I am using the CAPTCHA gem in my application and always got the following error: undefined method `stringFT'' for GD::Image:Class It turns out that I was missing the GD libs for ruby. I''m on ubuntu, so a quick sudo install libgd-ruby solved the problem for me. I also found resources for OS X and Red Hat Enterprise Linux 4: OS X: http://lukewarmtapioca.com/2007/02/06/gd-on-osx-and-ruby-stringft/ Red Hat: http://involution.com/2007/06/11/problems-with-rubys-captcha-gem/ -- Posted via http://www.ruby-forum.com/.