BACKGROUND Insulin resistance (IR) increases with advancing age, yet the underlying mechanism is not well established. Although adipocytokine retinol binding protein 4 (RBP4) was recently shown to be linked to IR, their relationship remains controversial and relatively little information exists regarding their roles in the elderly subjects. We investigated the association between RBP4 and IR in obese and nonobese elderly subjects. METHODS A total of 111 (68 nonobese and 43 obese) apparently healthy elderly subjects, aged 75.9+/-4.8 y were included. IR was determined by homeostasis model assessment (HOMA-IR). Serum RBP4 was measured by enzyme-linked immunosorbent assay. RESULTS In all subjects, RBP4 levels were positively correlated with fasting insulin, HOMA-IR, and triglycerides. However, after subgroup analysis, RBP4 levels were positively correlated with fasting glucose, fasting insulin, and HOMA-IR in the obese group only. In step-wise multiple linear regression analysis, RBP4 was found to be independently associated with triglyceride levels in the nonobese group and independently associated with HOMA-IR in the obese group. CONCLUSIONS The reason for the differing metabolic role of RBP4 in obese and nonobese elderly subjects remains uncertain, but our findings suggest that RBP4 may be linked to IR and lipid metabolism, at least in the elderly.