Colitis cystica profunda, although rare in occurrence, deserves recognition as a distinct pathologic entity. Several types of clinical presentation have been recognized, the most common being a solitary lesion in the rectum. The cause is generally ascribed to the reparative process associated with chronic mucosal inflammation. Differentiation of this entity from mucus-producing adenocarcinoma should be possible with an adequate biopsy. Conservative excision is appropriate therapy, depending on the clinical manifestations.