Several reports have shown elevated circulating beta-endorphin (beta-EP) levels in patients with polycystic ovarian disease (PCOD). However, it is not yet clear whether these high beta-EP levels are linked to the etiopathogenesis of PCOD or are secondary to the obesity. In the present study we measured beta-EP plasma concentrations in 19 PCOD patients, 10 with normal weight (Group A) and 9 with excessive weight (Group B), and in 18 normally ovulating women, 10 with normal weight (Group C) and 9 with excessive weight (Group D). beta-EP values were similar in the two groups of non-obese patients and controls. beta-EP concentrations were also similar in the two groups of obese patients and controls, and they were significantly higher (p less than 0.05) than in non-obese patients. Our data indicate that in PCOD, elevated beta-EP values are related to obesity, suggesting that they are not linked to the pathogenesis of PCOD.