On well defined criteria a total of 102 fiberoptic bronchoscopies (FB) were done on HIV-infected patients with pulmonary symptoms. A microbiological agent was identified in 85 patients (83%). Pneumocystis carinii (PC) was histologically verified in 61 patients, bacteria cultured in 22 patients, and cytomegalovirus (CMV) cultured in 17 patients. A histological diagnosis of CMV was only established in 2/17 patients. In the present study, a CMV positive culture from bronchial lavage fluid did not appear related to the clinical picture. Patients with P. carinii pneumonia (PCP) had significantly higher IgA, lower CD4-count, more commonly dyspnea and an X-ray showing diffuse interstitial infiltration than patients without PCP. Patients with bacterial pneumonia had significantly higher CD4-count, lower IgA, more commonly productive cough and an X-ray showing focal infiltration. In more than 75% of the patients, microorganisms identified were responsible for the pulmonary symptoms leading to bronchoscopy. Mainly PC and bacterial pathogens, both of which are treatable, were responsible for these infections. Pulmonary infections of clinical relevance besides PCP and bacterial infections were rare (3%, 95% confidence limit 1-8%).