A random sequential comparative study of three models of the Copper T intrauterine contraceptive device (IUD) was undertaken in 1,792 women. For 7 months, the TCu 300 and TCu 220C were randomly inserted, and then the TCu 380A and 220C were randomly inserted for the next 12 months. The log-risk method of life-table analysis of event rates was performed at the end of each of the first 3 years of use of each device. The TCu 380A had the lowest pregnancy rate during each year of use, although the difference was not significant. At the end of each of the first 2 years, the TCu 300 was removed significantly less than the TCu 220C and TCu 380A for bleeding and pain. At the end of three years, the rates of removal for bleeding and pain for the TCu 380A and TCu 300 were similar and lower than that for the TCu 220C, but the overall difference was not significant. There were no differences among the devices for any other relevant use-related reasons. The TCu 380A was removed for other medical reasons significantly more frequently than the other devices at the end of 2 and 3 years. Adjusting for parity did not alter the results. The findings of this study suggest that the copper sleeves along the horizontal arms together with copper wire on the vertical arm in the TCu 380A model provide greater protection against intrauterine pregnancy, whereas the copper sleeves along the vertical arm as in the TCu 220C caused increased removals for bleeding and pain. The TCu 380A should be studied in a larger number of patients for a longer period of time to determine its clinical effectiveness. It may become the IUD of choice for all women irrespective of parity.