A total of 1905 subjects were randomly allocated to four types of intrauterine devices (IUDs) and were observed for 45,683 woman-months of use. While no method failure was observed with levonorgestrel (LNG) IUD, 11 women became pregnant with other devices; 4 with Copper T 380Ag, 1 with Copper T 220C, and 6 while using Copper T 200B, indicating method failure rates of 1.0, 0.3 and 1.6, respectively, at 36 months of use. These rates were within acceptable range. Continuation rates were significantly lower with LNG IUD (74.5, 58.7, 38.8 at 1 year, 2 years and 3 years, respectively) as compared to other copper devices, which ranged between 82.4 to 84.4 at 1 year, 66.6 to 69.9 at 2 years and 45.4 to 50.4 at 3 years. The difference in continuation rates was mainly due to menstrual disturbances (e.g. amenorrhoea, irregular bleeding) which were higher with LNG IUD (27.9 per 100 users) as compared to the copper devices (13.4-15.4 per 100 users) at 36 months of use. The risk of expulsion ranged between 8.3 to 10.6 per 100 users and was comparable for all the devices. The observations from the present study based on 36 months of experience with different intrauterine devices do not indicate the need to replace CuT 200, the device currently in use in the National Programme.