Forty-six patients with positive sputum cultures for Mycobacterium avium complex and cavitary disease were placed on a 4-drug regimen consisting of isoniazid, rifampin, and ethambutol daily and streptomycin twice weekly. Forty-two (91.3%) converted their sputum to negative and 4 (8.7%) failed to convert. All of the 4 nonconverters had prior subtotal gastrectomy. Twenty-two patients were available for long-term follow-up: 12 patients completed 24 months of chemotherapy, all experienced sputum conversion, but 2 reactivated, 1 at 9 and the other at 27 months after termination of chemotherapy. These 2 patients had prior subtotal gastrectomy. Ten patients completed 18 months of chemotherapy with sputum conversion, 2 of these reactivated but had not had prior subtotal gastrectomy. In this group of patients, subtotal gastrectomy appeared to be an adverse risk factor for both initial treatment response and reactivation in pulmonary disease caused by Mycobacterium avium complex.