Aim: Serum gamma-glutamyl transferase (GGT) activity changes in response to oxidative stress. Metabolic syndrome (MetS) is associated with an increased risk of major cardiovascular events. Few data are available on the association between serum GGT and the prevalence of MetS among community-dwelling individuals in Japan. Methods: We recruited 793 men (mean age, 60 14 years), and 1,073 women (62 12 years), free from any history relating to cardiovascular disease during their annual health examination, from a single community. We performed a cross-sectional study to examine whether serum GGT was associated with MetS. Results: The levels of most confounding characteristics varied with increasing GGT activity. After adjustment for age, smoking status, drinking status, low-density lipoprotein cholesterol, uric acid, estimated glomerular filtration rate and alanine aminotransferase, the odds ratios (95% confidence interval) for MetS increased across serum GGT tertiles (