The relationships between increases in body mass index (BMI) and increases in hypertension were compared between non-drinkers with elevated serum γ-glutamyl transpeptidase (γ-GTP) levels (≥50 U/I) and those with normal levels, who comprised 10,952 men and 22,107 women aged 40–59 years recruited from an occupational health clinic. Hypertension was found in 16.1% and 13.5% of the men and women, and elevated serum γ-GTP was found in 10.8% and 2.8% of the men and women, respectively. The prevalences of hypertension and elevated serum y-GTP levels were both increased with increased BMI. Hypertension was, however, shown to be 1.5 times more prevalent in the persons with elevated serum γ-GTP levels than in those with normal levels in both sexes, even after adjusting for BMI by a multiple logistic analysis. It can be concluded that elevations of serum γ-GTP, which are probably a reflection of fatty liver in the non-drinkers, are closely related to the development of hypertension associated with increased obesity.