Four principal colony types of gonococci have been previously described, and it has been shown that primary isolates from the urethra and cervix are primarily of colony types 1 and 2. In the present work, gonococcal isolates from the rectum were also shown to be predominantly colony types 1 and 2. Visualization and typing of gonococcal colonies in primary rectal isolates were facilitated by the use of medium containing vancomycin, colistin, nystatin, and, in some cases, trimethoprim lactate. Control experiments showed that these agents sometimes caused minor alterations in colonial morphology; but with knowledge of these alterations satisfactory colonial typing could be made.