A comparative evaluation of the Lippes loop TCu-200 and the Dalkon Shield intrauterine devices inserted under controlled conditions is presented. 1-year continuation rates (78-82.4 per 100 acceptors) and pregnancy rates (2.1-3.1) did not differ significantly though expulsion rates were considerably higher for the Lippes loop (5.8 per 100 acceptors) compared to the TCu-200 (1.8) and the Dalkon Shield (1.7). The removal rates (12.9-14.1 per 100 acceptors) and reasons for removal were similar for all 3 devices. Generally continuation rates increased and pregnancy and expulsion rates decreased with increasing age and/or parity with each of the devices. The results indicate that the increased demographic effectiveness of the Dalkon Shield and TCu-200 devices depend upon their low expulsion rates.