RBP4 levels were significantly higher in patients with metabolic syndrome and type 2 diabetes than in euglycemic subjects (42.9±14.6; 42.3±17.0 and 37.4±11.7 μg/ml, respectively) and correlated with triglycerides but not with those of HOMA-IR in the whole population. This evidence concerns the gene RBP4 and type 2 diabetes mellitus.