Forty-five bronchoalveolar lavages (BAL) were performed in Brazzaville in AIDS patients who did not expectorate acid- and alcohol-resistant bacilli (AARB). All patients presented with respiratory symptoms (cough, dyspnoea or chest pain), and all but 6 of them had abnormal radiography of the chest. Four cases of pneumocystosis were diagnosed (9%); 3 of these patients had interstitial pneumonia and dyspnoea. No AARB was found at microscopic examination of BAL which showed Pneumocyctis carinii; no culture on Löwehstein's medium could be made. The authors consider that the low prevalence of pneumocystosis in Africa, compared with industrial countries, is due to a smaller dissemination of the parasite in Africa rather than to immunodepression which is known to be more pronounced in AIDS patients from industrial countries.