A case of primary peritoneal nocardiosis is presented. The patient died, despite prompt, aggressive and appropriate antibiotic therapy. Decreased patient resistance is suggested as the cause of the overwhelming nature of the infection in this case. The importance of administering prophylactic antibiotics on a long-term basis to prevent recurrence after successful treatment is stressed. Although nocardial infections are rare, they may become more common because of the current widespread use of immunosuppressive therapy.