It is well known that leptin, the ob gene product, is involved in the regulation of food intake and thermogenesis. Recent studies also demonstrate that leptin may be able to modulate functions of cells involved in nonspecific immune response such as phagocytosis and secretion of cytokines by macrophages. This and the prominent implication of polymorphonuclear neutrophils (PMNs) in infectious response suggested a possible role of leptin as a modulator of PMN functions. We detected a leptin receptor on the PMN membrane by immunocytochemistry with an anti-leptin receptor. Using chemiluminescence we then demonstrated that leptin enhances oxidative species production by stimulated PMNs. These results show for the first time that a functional leptin receptor is present on PMNs and that leptin may be able to influence their oxidative capacity.