Liver biopsies were taken from ten AIDS patients. Liver architecture was normal in all patients. On 1-micron-thick sections stained with toluidine blue, all ten cases showed lipid overload of perisinusoidal cells (1 massive, 5 moderate and 4 mild) compared to 2/8 in control patients, who had mild lipid overload. Other sinusoidal abnormalities such as hypertrophy of Kupffer cells and inclusions in endothelial cells were also noticed. Some hepatocytes presented evidence of cellular damage. Perisinusoidal cell lipid overload was not associated with hypervitaminosis A. We hypothesize that the abnormal accumulation of lipids in perisinusoidal cells (non-induced by hypervitaminosis A) in patients with AIDS could be due to defective transport of vitamin A from perisinusoidal cells to hepatocytes, and/or from hepatocytes to blood. The cause of the defect is unknown. Since lipid overload occurs in many and diverse conditions (diabetes, cholestasis, primary biliary cirrhosis, etc.), it seems reasonable to propose that the defect is non-specific and limited to functional or structural damage of the liver whether induced by drugs, liver or systemic diseases.