The outcome of 57 surgically treated cases with pulmonary infection due to Mycobacterium xenopi was studied. Success without any complications was observed in 21 patients while complications were observed in the other 36, during the 1st year (early complications) after surgery in 26 patients and after the 1st year (late complications) in 10. Early complications included two deaths, four relapses, two treatment failures, six cases of respiratory impairment, four cancers and 21 immediate post-operative complications which required 19 supplementary operations. Early complications were more frequent (p less than 0.05) in patients with pleural and/or emphysematous lesions. Late complications included 10 deaths, eight relapses, four pulmonary infections and five cancers. They were more frequent (p less than 0.05) in patients with the following risk factors: under nutrition, smoking/alcohol abuse, gastric ulcers with or without gastrectomy, associated serious illness, respiratory impairment and extensive pre-surgical radiographic lesions. In no case was infection due to M. xenopi directly responsible for lack of improvement.