The study of bone density in long-term DMPA users is reported. The aims were to study and compare bone density in long-term DMPA users with intrauterine device (IUD) users. Fifty current users of DMPA with a minimum 36 months previous use were compared to 50 current IUD users as control. The bone mineral density was measured by dual energy x-ray absorptiometry (DEXA) at the non-dominant distal and ultradistal forearm. Serum estradiol was measured by microparticle enzyme immunoassay technique in both groups. Age, income, weight, height, BMI, and parity of both groups were matched. The mean bone mineral density of distal forearm in DMPA and IUD users was 0.48 +/- 0.05 g/cm2 in both groups. The mean bone mineral density of ultradistal forearm was 0.38 +/- 0.06 g/cm2 in DMPA users and 0.4 +/- 0.05 g/cm2 in IUD users. No differences in mean bone mineral density of distal and ultradistal forearm between DMPA and IUD users was demonstrated (95% CI -0.02, 0.02 and -0.04, 0.001, respectively). However, the serum estradiol levels were significantly different between DMPA and IUD users (95% CI -122, -68.1). From this study, it is suggested that long-term DMPA use should not have any adverse effect on bone density even if it reduces serum estradiol.