Thirty patients with lung involvement with Pneumocystis carinii and other opportunistic organisms, many of whom also had Kaposi sarcoma, were seen from December 1980 through March 1982. Clinical manifestations consisted of a prodrome of weeks to months with weight loss, fever, and malaise. When clinical pneumonia became apparent, four distinct radiographic patterns were identified. Pneumocystis carinii was uniformly present, and the most common pattern encountered was a relatively symmetric, homogeneous perihilar pneumonia that progressed to diffuse consolidation. Asymmetric and focal infiltrates were seen in patients who proved to have concomitant opportunistic infection, most commonly fungal in all but two cases. A third pattern of nodular and linear densities with or without adenopathy was seen in patients without pneumonia who had biopsy-positive Kaposi sarcoma involving the lung parenchyma. A fourth pattern represented a combination of any of the first three, and these patients had multiple infections as well as Kaposi sarcoma in the lung. Any significant change in the radiograph indicating progression of disease while on therapy prompted a rebiopsy, and in five of 10 patients other infections and/or Kaposi sarcoma were identified.