It has been reported that polycystic ovary syndrome (PCOS) is very frequently associated with obesity, insulin resistance and hyperinsulinemia. However, metabolic disorders may lead to suppression of reproductive hormone secretion during undernutrition and in obesity. Some neuropeptides, such as neuropeptide Y (NPY) and galanin, modulate the control of appetite and play an important role in the mechanism of luteinizing hormone-releasing hormone (LHRH) secretion. NPY and galanin regulate appetite via both central and peripheral mechanisms. The interaction between central and peripheral signals for the control of food intake is due to leptin. Leptin can modulate the activity of NPY and other peptides in the hypothalamus that are known to affect eating behavior. In order to evaluate the relationship between NPY, galanin and leptin, 28 women with PCOS, 32 obese women (non-PCOS) and 19 lean healthy women (control group) were investigated. Obese women with PCOS were divided into two groups: PCOS (A) overweight (body mass index, BMI 26-30 kg/m2), and PCOS (B) obese (BMI 31-40 kg/m2). Plasma NPY, galanin and leptin concentrations were measured by radioimmunoassay. Plasma leptin levels in obese women with PCOS (groups A and B) were significantly higher than those in the control group (p < 0.05, p < 0.05, respectively). A significant positive correlation between plasma leptin and BMI in women with PCOS was found (r = 0.427, p < 0.01). A positive correlation was demonstrated between leptin and testosterone in PCOS (r = 0.461, p < 0.01). Plasma galanin concentrations in PCOS were higher than in the control group but the differences were not significant. Plasma NPY levels were significantly elevated in both non-obese (normal) and obese women with PCOS (group A) (p < 0.01, p < 0.005, respectively). However, in obese non-PCOS women plasma NPY levels gradually increased with increase in BMI. No significant correlations were found between galanin, NPY and percentage change in response of LH to LHRH, as well as between NPY and insulin, and galanin and testosterone. Plasma insulin concentrations in women with PCOS (group B) were significantly higher than in the control group (p < 0.001). Increased plasma NPY levels are found in both obese and non-obese women with PCOS. The increase in NPY is independent of the increase in BMI. In obese women with PCOS, plasma leptin is increased compared with control lean women. Serum insulin concentration is increased in obese women with PCOS. A positive correlation exists between leptin and BMI as well as between leptin and testosterone in women with PCOS. These results may suggest that the feedback system in the interaction between leptin and NPY is disturbed in PCOS.