The clinical performance of the Copper T380A (TCu380A) and the Multiload 250 (MLCu250) intrauterine devices (IUDs) were evaluated for 12 months in a group of women who had one of the two IUDs inserted. Results are from a randomized clinical trial conducted at four collaborating research sites located in three developing countries. The gross cumulative life-table pregnancy rate of the TCu380A IUD was significantly lower than the rate with the MLCu250 IUD at 12 months (0.5 and 1.2, respectively, p < 0.01). No statistically significant differences between the two study IUDs were found with regard to IUD expulsion or IUD removal due to bleeding/pain, personal reasons, medical reasons, or planned pregnancy. TCu380A IUD users were more likely to report experiencing increased dysmenorrhea (p < 0.01) or intermenstrual pelvic pain (p < 0.01) than were MLCu250 IUD users. However, few of these users discontinued use of their assigned IUD because of having experienced menstrual bleeding disturbances or intermenstrual pelvic pain. These data indicate that the TCu380A IUD may be a better option than the MLCu250 IUD for women wishing to practice highly effective long-term birth control without having to resort to hormonal methods.