Runyon group IV atypical mycobacteria, Mycobacterium fortuitum, is an environmental organism and is capable of producing a variety of clinical infections such as cutaneous infection, abscess and pulmonary and ocular infection. Rarely, it has been a documented cause of peritonitis in patients receiving continuous ambulatory peritoneal dialysis (CAPD). We report a case of M. fortuitum peritonitis in a patient undergoing CAPD and emphasize the importance of mycobacterial cultures in patients with CAPD-associated peritonitis whose routine culturing yields no organisms repeatedly.