Serum sex hormone levels were measured preoperatively in 57 morbidly obese patients (19 men and 38 premenopausal women) and 12 months after vertical banded gastroplasty. In the male group, there was a significant decrease in estradiol and an increase in follicle-stimulating hormone (FSH), total testosterone and sex-hormone-binding globulin (SHBG). Among female patients, a significant decrease in estradiol, total and free testosterone and an increase in FSH and SHBG was found. Irregular menses present preoperatively in 5 women were corrected after successful weight loss. In conclusion, altered sex hormonal levels and gynecologic abnormalities associated with morbid obesity are corrected with adequate weight loss following vertical banded gastroplasty.