Liver fibrosis was observed in non-alcoholic, non-diabetic obese patients with fatty liver. The extent of fibrosis was more severe in patients who were obese for a long time and had severe fatty deposition in the liver. Laboratory data were not useful for differentiating between fatty livers with and without liver fibrosis. The results suggested that fatty liver in obese patients should be treated by weight reduction in order to prevent the progression of liver fibrosis.