Apelin (AP), a novel peptide, is an endogenous ligand for the G-protein-coupled receptor, APJ. AP and APJ mRNA have been found to have a widespread distribution in both the central nervous system and the peripheral tissues. AP and its receptor has also been detected in the arcuate and paraventricular nuclei of the hypothalamus, which are involved in the control of feeding behavior and energy expenditure. It is reported that intracerebroventricular (icv) injection of AP-13 caused a decreased food intake in fed but not in fasted rats, while daytime administration of AP-12 stimulated feeding. Considering the controversy, the physiological significance of these findings is unclear. The present study was designed to investigate the effects of chronic peripheral administration of AP-13 on food intake, water intake and body weight in rats. The animals (Spraque Dawley rats, male, 180-200g) were adapted to metabolic cages for a period of 5 days before the experiments. AP-13 [30, 100 and 300 µg/kg (per group, n=8)] or vehicle was administrated i.p. for 10 days at the onset of the dark cycle. Metabolic measurements were performed at 24 hours after vehicle or AP-13 administration. All data are reported as mean values ± SEM, compared by ANOVA. Metabolic measurements revealed that AP administrated groups had significant increase food intake (17.2±0.2, 18.0±0.2, 18.2±0.2g. per 100g body weight, respectively; AP30, AP100, AP300) compared with the vehicle (16.2±0.3) but not in body weights. Additionally AP treated groups had increased water intake (8.2±0.1, 8.0±0.1, 8.1±0.1 ml per 100g body weight, respectively) compared the vehicle (7.3±0.1). Our data suggest that AP-13 is a peptide that stimulates food and water intake in rats. AP may have an important role between peripheral and central mechanisms involved in feeding. So that, the understanding the exact role of AP-13 in regulation of food intake and body weight control is fundamental to establishing effective therapies for obesity.