Some fans of the Call of Cthulhu roleplaying game prefer to use the GURPS system. Although there is no official conversion of CoC to the current 4th Edition of GURPS, it is easy to convert materials written for Chaosium's BRP system. This fan-created guide explains how.
There was also an official conversion written for the now out-of-print 3rd Edition GURPS rules,, called GURPS CthulhuPunk. It was set in a dark cyberpunk future.