The effects of weight reduction on hepatic test results and physical findings related to the liver were retrospectively evaluated in 39 overweight patients screened to exclude other factors affecting the liver. An additional 11 overweight patients with primary liver disease were retrospectively evaluated to compare the effect of weight reduction in patients with liver disease with its effect in those without primary liver disease. This study showed that in overweight adults without primary liver disease, a weight reduction of greater than or equal to 10% corrected abnormal hepatic test results, decreased hepatosplenomegaly, and resolved some stigmata of liver disease. In similarly studied overweight patients with primary liver disease, some findings improved, but the changes did not correlate with a greater than or equal to 10% weight loss. Increased alanine aminotransferase activity was the most frequent hepatic enzyme abnormality in this population. For every 1% reduction in body weight, alanine aminotransferase activity improved by 8.1%. After other causes of liver disease are eliminated by clinical and biochemical parameters, weight reduction should be tried for overweight patients with abnormal hepatic test results in the absence of obvious primary liver disease as judged by clinical and biochemical parameters before extensive and expensive studies are undertaken.