The present one-year prospective study was performed to evaluate the effects of an oral contraceptive containing 20 mcg ethinylestradiol plus 0.150 mg desogestrel on bone metabolism in young women. Nineteen women aged 20 to 30 years completed the trial. Bone density was measured in the distal radius by dual photon absorptiometry before starting pill use and at the 3rd, 6th and 12th cycle. At the same time intervals, urinary hydroxyproline-to-creatinine ratio and serum alkaline phosphatase were evaluated. Bone density showed a slight, but not significant, increase at the end of the trial. Both urinary hydroxyproline-to-creatinine ratio and serum alkaline phosphatase showed a significant decrease. The results suggest that bone resorption is reduced, although bone density in the distal radius is not significantly increased in young women using an oral contraceptive containing only 20 mcg ethinylestradiol for one year.