Call of Cthulhu is a horror fiction role-playing game based on H. P. Lovecraft's story of "The Call of Cthulhu" and HP Lovecraft's Cthulhu Mythos. First released in 1981, the system has seen several releases over the years.
The sixth edition only had minor changes from the fifth edition.
The sixth edition first was released as a hardcover in 2004, then later as a softcover in 2005.