From the back of the first-printing US boxed set:
| Eldritch Horrors!
| “…its rugose, dead-eyed rudiment of a head swayed drunkenly from side to side. Its forepaws were extended, with talons spread wide, and its whole body was taut with murderous malignity.”
| —H. P. Lovecraft
Enter the awesome universes of the Cthulhu Mythos, those dread tales in which magic, science, arcane lore, and dark destinies irrevocably sear the lives of those for whom the bizarre and the curious have unseemly attraction.
Specially designed to portray the situations and denizens of the Mythos, CALL OF CTHULHU uses a variant of the BRP system, adding characteristics for Sanity and Education. The first book included is Basic Role-Playing itself.
The second (and by far the largest) book is Call of Cthulhu, which explains the characteristics, skills, occupations, and resources available to Investigators, the many beings specific to the Mythos (deep ones, flying polyps, dimensional shamblers, shantaks, cthonians [sic], Cthulhu, Yog-Sothoth, etc.), full rules for magic and the use of the famous books (the Necronomicon, De Vermiis Mysteriis, Unaussprechlichen Kulten, etc.) which have fascinated readers for decades. This book translates the Mythos fiction into FRP terms. Scenarios are drawn in the style of Lovecraft, not directly from specific stories.
The third book is A Sourcebook for the 1920’s [sic], consisting of non-Mythos data–price lists, plans, maps, distances, thumbnail biographies, as well as garden-variety monsters upon which budding Investigators can sharpen their skills.
There are character and monster silhouettes for play, record sheets, a world map of ‘dig’ sites, and six dice: 1D4, 3D6, 1D8, and 1D20.
The first printing of Call of Cthulhu contains an updated edition of rules of the Basic Role-Playing system, a 96-page Call of Cthulhu rulebook expanding on the BRP system, A Sourcebook for the 1920s (32 pages), an 8-panel fold-out world map, a book of character sheets, cardstock figures to be cut out, and a set of dice, all in a 2-inch-deep box. (The second printing includes the same contents in a 1-inch-deep box.)
The Call of Cthulhu rulebook includes information on the background setting, character creation, available skills, character sanity control, Cthulhu creatures and mythos, magic, scenarios, and area maps.
A Sourcebook for the 1920s includes information on timelines, biographies, companies, crime, railway coaches, travel, price charts, weapons, and beasts and monsters.
The books and map are printed in umber (brown) ink.
The game uses a simplified version of Chaosium's Basic Role-Playing system.