As slight abnormal values of serum GOT and GPT levels are observed very often in health examinations, we studied the effects of overweight or habitual drinking on the two transaminase levels using data from health examinations of male clerical workers aged 40-54.The serum GPT level had a linear positive correlation with the obesity index (p 0.1). The condition in which the serum GPT level exceeds the serum GOT level (GOT/GPT<1) and both of them are less than 100 units, was found to be largely due to overweight or obesity. The condition in which the serum GOT level exceeds the serum GPT level and the former is moderately elevated in the range of 30 to 100 units, was strongly associated with heavy drinking.We conclude that effective guidelines, based on slight changes in serum transaminase levels, can be provided to obese individuals or drinkers in order to prevent advanced liver cell injuries.