Background: Serum γ-glutamyltransferase activity (GGT), even when within its normal reference range, catalyzes low density lipoprotein oxidation in vitro and predicts cardiovascular events. Of the four GGT fractions (b-GGT, m-GGT, s-GGT, and f-GGT) recently identified in blood, only b-GGT is found within atherosclerotic plaques. Our goal was to identify the determinants of the GGT fractions (b-, m-, s-, and f-GGT) and their association with established cardiovascular risk factors in healthy subjects. Methods: Multiple linear regression analysis was applied to estimate the association of fractional GGT with gender, age, body mass index, arterial pressure (AP), plasma glucose, alanine aminotransferase (ALT), high and low density lipoproteins (LDL-C) cholesterol (HDL-C), triglycerides (TG) and C-reactive protein (CRP) in 200 healthy subjects. Results: All GGT fractions were associated with ALT; b-GGT with AP, TG, and CRP; m-GGT with LDL-C, TG and CRP; s-GGT with TG and CRP, and f-GGT only with LDL-C, whereas gender was associated with s-GGT and f-GGT only. Conclusions: In healthy individuals, cardiovascular risk factors are associated with high molecular weight GGT fractions, namely with b-GGT, the only form present within the plaque. This finding adds to the present knowledge concerning the relevance of GGT, within its reference range, for atherosclerosis-related events. Clin Chem Lab Med 2010;48:713–7.