Dehydroepiandrosterone (DHEA) is an adrenal hormone reported to prevent body weight gain, diabetes mellitus and atherosclerosis. We hypothesized that DHEA is involved in the pathophysiology of non-alcoholic fatty liver disease (NAFLD) often associated with obesity and insulin resistance. In this study, we aimed to examine the clinical significance of serum DHEA sulfate (DHEAS) in patients with NAFLD.We determined serum DHEAS, serum alanine aminotransferase (ALT), serum lipids, plasma fasting glucose and insulin levels in 158 Japanese men who had neither viral hepatic diseases nor alcohol intake exceeding 20 g/day. NAFLD was diagnosed by the presence of fatty change of the liver by echotomographic examination.Among the study subjects, 69 were diagnosed as having NAFLD. Their serum DHEAS levels were significantly higher than in 89 subjects without NAFLD. Serum DHEAS levels in 19 NAFLD patients with elevated ALT levels (>40 U/L) were significantly higher than in the other 50 NAFLD patients with normal ALT levels (≤40 U/L). Multivariate regression analysis demonstrated that serum ALT was positively correlated with serum DHEAS, serum triglyceride and body mass index.Serum DHEAS levels are increased in patients with NAFLD with elevated ALT levels. Increased serum DHEAS may be a component of the pathophysiology of NAFLD.