Mycobacterial peritonitis is rare among patients undergoing peritoneal dialysis. It is usually caused by group IV environmental mycobacteria. We report three such cases and review the literature on this subject. Negative results in routine bacterial cultures and persistent peritonitis may be the only clues indicating the presence of mycobacterial infection. The lack of specific symptoms and signs as well as inadequate culture techniques may delay diagnosis. Multiple cultures of centrifuged dialysis fluid may be required for isolation of the organism. Peritoneal biopsy may yield additional diagnostic information. Management frequently entails removal of the dialysis catheter in addition to antimicrobial therapy. Significant morbidity may ensue if treatment is delayed. Amikacin--with or without another antibiotic--provides adequate coverage.