In AIDS patients infectious pulmonary complications may very frequently be demonstrated by both biopsy and autopsy. Bacterial pneumonias occur much more frequently than classic opportunistic infections, e.g. P. carinii pneumonia. Usually, several complications are present concomitantly which impairs diagnosis as well as therapy. Increased survival and modern therapeutic modalities change the spectrum of AIDS-associated pulmonary complications as well as their morphology. In the present study pulmonary complications are directly responsible for the patients' death in more than 70% of the cases.