OBJECTIVE: To determine the incidence, clinical characteristics, microbiological features and outcome of Mycobacterium xenopi infections in patients attending a university hospital. METHODS: We reviewed the files of HIV-seronegative patients meeting ATS criteria for M. xenopi pulmonary infection between 1993 and 2004. RESULTS: Ten patients were studied (7 men, 60+/-27 years). All but one had underlying chronic health disorders (chronic lung disease, cancer, alcoholism, systemic steroid therapy). The clinical and radiological findings were those associated with tuberculosis. Acid-fast bacilli were detected by direct examination in 9 cases, and antituberculous treatment prescribed in 8 patients. Specific treatment was started an average of 60+/-25 days after sampling, and generally combined a fluoroquinolone, clarithromycin and rifampicin, with or without ethambutol, for a mean of 11.4 months (1-37 months). Five patients had surgical excision (diagnostic in 1 case). Four patients died of their underlying disease. Two patients recovered with antibiotics alone and three with antibiotics and surgery. One patient was lost to follow-up after five months. CONCLUSION: Pulmonary infection by M. xenopi is rare in HIV-seronegative patients. The prognosis depends mainly on the patient's underlying health status. Surgery is an important component of treatment.