cl-cffi-gtk is a Lisp binding to GTK+ 3 (GIMP Toolkit) which is a library for creating graphical user interfaces. cl-cffi-gtk is licensed using the LGPL which has been adopted with a preamble that clarifies the terms for use with Lisp programs and is referred as the LLGPL. This work is based on the cl-gtk2 library which has been developed by Kalyanov Dmitry and already is a fairly complete Lisp binding to GTK+. The focus of this work is to document the library more complete and to do the implementation as consistent as possible. Most informations about GTK+ can be gained by reading the C documentation. Therefore, a modified version of the C documentation from http://www.gtk.org is included into the Lisp files to document the Lisp binding to the GTK+ library. The API documentation is available online at http://www.crategus.com/books/cl-cffi-gtk/ Examples of the usage are included in a gtk-demo and tutorial examples. Start with the tutorial available online at http://www.crategus.com/books/cl-gtk/gtk-tutorial.html to learn how to use the library. Look at the wiki at http://github.com/crategus/cl-cffi-gtk/wiki for news about the development of the library. At this time, the library is developed and tested with SBCL 1.1.9 on a Linux system (Ubuntu). Futhermore, the library is tested with Clozure Common Lisp 1.9 and CLISP 2.49 on Linux. The minium version requirements are GTK+ 3.4 and GLIB 2.32. The library compiles and runs under Windows 7, but when moving an application window the application will freeze. This bug is not solved at this time.