This report summarizes the results of an 8-year study of the treatment of non-tuberculous mycobacterial infections and the long-term efficacy of this treatment in patients without AIDS. Of 25 patients, aged 10-82 years, 24 had pulmonary involvement; in 5 cases as part of disseminated disease. One patient had a renal infection only. Predisposing factors were identified in 16 patients. M. avium-intracellulare and M. malmoense were isolated in 17 and 7 patients, respectively, and M. kansasii in 1 patient. Three patients were subjected to lobectomy and 22 received multiple drug chemotherapy for 18-60 months. Chemotherapy was initially effective in 17/22 patients and surgery in 3/3. However, in the end 10 patients died of their mycobacterial infection, and 6 are still suffering from chronic infection. Only 7 patients appear to be free of disease more than 2 years after completing chemotherapy.