Sixty females, aged 20 to 35, received an oral contraceptive pill (Norgestrel 0.5 mg and Ethinyloestradiol 50 micrograms/day) during one year. Group I was formed by 41 normal patients before and after 12 months. Group II was formed by 11 patients, normal before and with impaired oral glucose tolerance after 12 months. Group III was formed by 8 patients with impaired glucose tolerance before treatment and normal oral glucose tolerance after 12 months. All patients were submitted to 3 oral glucose tolerance tests, the first one at the 16th day of the control cycle, the second and the third at the 16th days of the 6th and 12th cycles during treatment. No significative modification of glycemia, insulinemia or weight was noted in group I. In group II the impaired oral glucose tolerance was associated with an increase of weight. In group III the improvement of glucose tolerance was marked by hyperinsulinemia.