Serum profiles of lipids and/or liver enzymes are established markers for the estimation of insulin resistance and diabetic risk in the non-diabetic middle-aged population. To identify prediabetic markers in young subjects, 110 young male subjects (20-29 years of age) with normal glucose tolerance (NGT) were divided into two groups by median body mass index (BMI), <22.18 (n=55) and ≥22.18 (n=55) kg/m(2). Indices of insulin sensitivity including HOMA-IR and ISI composite, indices of β-cell function including HOMA-β, insulinogenic index (ΔI(30)/ΔG(30)) and ΔI(30)/ΔG(30)/ HOMA-IR were calculated. Statistical associations between these parameters and the serum lipid profiles and liver function were evaluated. Alanine aminotransferase (ALT), γ-glutamyltransferase (GGT), total cholesterol (TC) and triglyceride (TG) levels were inversely correlated with the ISI composite among individuals with BMI ≥22.18 kg/m(2) but not those with BMI <22.18 kg/m(2). Multivariate regression analysis revealed that, in Group N, the plasma glucose levels at 60 min (PG(60)) were inversely correlated with the ISI composite and the insulinogenic index, and were positively correlated with the GGT, TC and TG levels. On the other hand, in Group L, PG(60) was correlated with the insulinogenic index, TC and TG levels. In conclusion, elevated levels of GGT, TC and TG are good clinical markers to predict diabetic risks, even in young NGT males. Of these, GGT was the most strongly related factor among subjects with relatively high BMI.