pkg-config is a script to make putting together all the build flags when compiling/linking a lot easier. Report bugs at http://bugzilla.freedesktop.org/ To use pkg-config, do something like the following in your configure.ac PKG_CHECK_MODULES([GNOME], [gtk > 1.2.8 gnomeui >= 1.2.0]) This puts the neccesary include flags to compile/link something against libgnomeui and all its dependencies in $(GNOME_CFLAGS), and the -L/-l flags for linking in $(GNOME_LIBS). Users can define the PKG_CONFIG environment variable to point at the right one, or if they cross-compile and have a correctly named pkg-config (eg. arm-linux-pkg-config) in their PATH that will be used in preference. Users can also define the GNOME_CFLAGS and GNOME_LIBS environment variables if they think they know better, pkg-config will not be called if they do that. The "gtk > 1.2.8" part is only neccesary if you want to specifically check if libgtk is version 1.2.8 or higher. Otherwise, the flags for gtk will be included automatically, since libgnomeui depends on gtk. So you could just say: PKG_CHECK_MODULES([GNOME], [gnomeui]) for any version of gnomeui. For more info, there's even a man page, try 'man pkg-config'