To evaluate the correlation between clinical and autopsy findings in 250 AIDS patients. Clinical and autopsy diagnoses of AIDS-defining diseases in 250 AIDS patients who died in Milan between May 1984 and February 1991 were compared. Pneumocystis carinii (PCP) and oesophageal candidiasis were the most frequent clinical diagnoses, while cytomegalovirus (CMV) infection was observed in almost half of the autopsies. Forty-seven per cent of the diseases found at autopsy had not been diagnosed during life; CMV infection, mycoses, HIV-specific brain lesions, cerebral lymphomas and progressive multifocal leukoencephalopathy (PML) had a higher rate of non-diagnosis in life. CMV visceral infection accounted for the majority of the diseases not recognized in life. In contrast, clinically diagnosed PCP, oesophageal candidiasis and, to a lesser degree, brain toxoplasmosis were often not found at autopsy, possibly indicating a significant rate of recovery and prevention of relapse. Finally, bacterial pneumonia and sepsis, although not AIDS indicator diseases, were observed in approximately one-third of the autopsies. Considerable differences in the frequency and type of the AIDS-defining diseases diagnosed during life and at post mortem were found.