Nocardia asteroides was isolated in 9 patients between June 1982 and February 1984. Clinical manifestations included acute pneumonia (3 cases), chronic lung abscess (2 cases, one of them requiring exploratory thoracotomy) and relapsing infection of the lacrimal canaliculus (1 case). Sputum or bronchial secretions were positive in 3 other patients without evidence of pneumonia, which could represent either an asymptomatic carrier state or a mild bronchial infection. Seven patients had one or several conditions known to favour Nocardia infection, the most frequent being steroid therapy (4 cases), while 2 patients had no predisposing factor. In our series of 5 nocardial lung infections, 2 patients had positive blood cultures. This quite unusually high rate may be related to the use of diphasic bottles and to our systematic policy of prolonged examination of blood cultures taken from immunocompromised patients. Cotrimoxazole was used as the first choice antinocardial agent.