We have evaluated an usefulness and association between serum levels of gamma-glutamyltranspeptiase (GGT) and metabolic syndrome (MS) in 40-year-old men and women. The prevalence of MS in men (11.8%) was higher than that of women (4.0%). Serum levels of GGT were higher in men and women with MS than in them without MS. In the prevalence of higher serum GGT, men group with MS (35.8%) was greater than women group with MS (22.7%). In the relative risk of MS to an increased level of GGT, women group was higher than men group (about 3 times) (female, OR=7.48 vs male, OR=2.46). The present study reveals that routine check of serum GGT in health examination can be useful for the prevention and management of MS including cardiovascular and/or liver diseases.