Objective: We sought to establish the lowest dose of 3-keto-desogestrel, when added to a copper-releasing intrauterine contraceptive device, that is needed to reduce menstrual blood loss to a very low level and to treat (essential) menorrhagia successfully. Study Design: A double-blind group comparative study was designed in which 203 healthy women with or without menorrhagia were enrolled and randomized to four different Multiload Cu250 intrauterine contraceptive devices, releasing 0 (control), 1.5, 3, or 6 μg of 3-keto-desogestrel daily. Menstrual blood loss, hemoglobin, and serum ferritin levels were determined before and during treatment. Results: All 3-keto-desogestrel–copper intrauterine contraceptive devices reduced menstrual blood loss significantly, causing a reduction of up to 30 to 40 mL after 12 months of use. All women with essential menorrhagia were considered to have been successfully treated after 6 months of use. Serum ferritin levels rose with all three 3-keto-desogestrel–loaded devices. Conclusion: A Multiload Cu250 intrauterine contraceptive device releasing 1.5 μg of 3-keto-desogestrel daily is able to reduce menstrual blood loss to a very low level and to replete body iron stores in women with or without menorrhagia. Higher doses have no superior effect. (Am J Obstet Gynecol 2000;182:575-81.)