Eight-hundred patients recruited between September 1981 and December 1984 were admitted to a randomized prospective trial of the Nova T (NTCu200Ag) and Multiload 250 (MLCu250) IUDs. At the cut off date, 31 December 1986, 206 patients had completed the 4-year trial period, 379 had terminated before completion and 215 were in the fourth year of use. For the third and fourth years, the MLCu250 had a significantly lower accidental pregnancy rate (p less than 0.05).