We reviewed the initial and follow-up chest roentgenograms (CXR) of 104 patients with the acquired immune deficiency syndrome (AIDS) and Pneumocystis carinii pneumonia (PCP) diagnosed between 1981 and 1985 in order to determine the relative frequencies of its various roentgenographic patterns. Although a diffuse bilateral interstitial infiltrate is most common, it was concluded that unusual and atypical roentgenographic manifestations of PCP occur in AIDS. These include localized infiltrate, cystic or honeycomb lesions, hilar enlargement and spontaneous pneumothorax.