BACKGROUND Mycobacterium fortuitum is an uncommon cause of soft tissue infections. Treatment is often inadequate with persistence of infection unless the aetiological agent and its antibiotic sensitivity are accurately established. METHODS Medical records of 23 patients with chronic soft tissue infection caused by M. fortuitum over a 12-year period from 1991 to 2002 were studied. RESULTS In 20 patients the cause was iatrogenic, following intramuscular injections (12), laparoscopy (5) and other surgical procedures (3) and in three patients discharging sinuses developed spontaneously. Patients presented with recurrent abscesses or chronic discharging sinuses that did not respond to conventional surgical drainage. The diagnosis was established by isolating M. fortuitum from the tissues in all cases. The treatment consisted of a more aggressive surgical intervention in form of excision, debridement and extensive lay open with curettage and prolonged administration of appropriate antibiotics. The organism showed maximum sensitivity to amikacin and ciprofloxacin. Healing occurred in all cases. Three patients suffered recurrences: two responded to further debridement and antibiotics and are well at 2 and 5 years, respectively. CONCLUSIONS A high index of suspicion based on clinical presentation is essential to diagnose M. fortuitum as a cause of soft tissue infection. Treatment involves aggressive surgical debridement and administration of combination antibiotics based on sensitivity, which should be continued for a period that will ensure complete healing and prevent recurrence.