Liver function and liver biopsy findings were studied in a selected group of 29 overweight patients. Fatty liver, fatty hepatitis, fatty fibrosis and fatty cirrhosis were seen with equal frequency. Diabetes was also present with an equal incidence in each of these four pathologic groups. Lipoprotein abnormalities, particularly type IV hyperlipoproteinemia, were found mostly in the two groups with the lesions with less fibrosis (fatty liver and fatty hepatitis). The pathologic picture resembled that of alcohol and postjejunoileal bypass-induced liver diseases suggesting a common denominator in these three conditions.