Literature on liver morphology in untreated obesity reveals varying prevalences of various pathological findings. The purpose of this literature study was to summarize and evaluate the published observations and to discuss discrepant findings. A complete search was aimed at utilizing bibliographic methods including a computerized survey. Forty-one original articles were included, comprising information on liver morphology in 1515 morbidly obese patients. Liver biopsy was considered normal in 12 per cent of the cases. The most frequent abnormality reported was fatty change, present in 80 per cent of the biopsies. Portal inflammation was also common (33 per cent). Fibrosis, mainly portal or periportal, was observed in 29 per cent. Cirrhosis, however, involved only 3 per cent. Study of relationships between the degree of liver change and certain possible pathogenetic factors (eg degree and duration of obesity, age, sex, alcohol consumption, diabetes mellitus) does not point towards a single causal factor. Co-influence of additional pathogenetic factors are likely in the development of liver changes in morbid obesity.