The WHO Special Programme of Research, Development and Research Training in Human Reproduction has conducted between 1979 and the present, three randomized comparative clinical trials of the TCu220C, Multiload 250, Nova T and TCu380A devices in 24 centres in 14 countries. The comparative study of the TCu220C and the Multiload 250 devices was completed after three years of use with no significant differences in event rates between the devices (three-year cumulative pregnancy rates of 1.7% and 2.8%, respectively). The Nova T device was discontinued from the comparative study with the TCu220C after five years of use having shown significantly higher cumulative pregnancy rates at three and at five years of use-6.6% and 12.3%, respectively, compared to 4.4% and 6.6%, respectively, for the TCu220C. In the comparative study of the TCu220C and TCu380A, the latter device had significantly lower cumulative pregnancy rates of 1.0%, 1.4% and 1.6% at three, five and seven years of use, respectively (comparative results for the TCu220C: 3.4%, 4.0% and 4.9%, respectively). It is suggested that the TCu380A life span be extended to at least seven years of use and the device be considered as a non-surgical, potentially reversible, alternative to tubal ligation for women needing long-term fertility regulation.