With the aim to evaluate the clinical performance of intrauterine devices (IUDs) especially designed for nulliparous women (TCu 380 Nul and ML Cu 375 sl), a prospective randomized, single-blind study comparing them with standard TCu 380 A, was carried out. We included 1170 healthy nulliparous women randomly allocated to receive any of the three types of IUDs and conducted follow-up for 1 year of use. Continuation and termination rates were evaluated by gross cumulative life table analysis and compared by the log-rank test. Continuation rates (95% confidence interval) at the end of the study for TCu 380 A, TCu 380 Nul and ML Cu 375 sl were 29.5% (+/-12.9), 85.9% (+/-5.3) and 85.4% (+/-5.8), respectively (p < 0.001). There were six pregnancies during the first 3 months of use, for a failure rate of 1% (+/-0.6) in the TCu 380 A group, 0.5% (+/-0.3) in TCu 380 Nul, and no pregnancy in ML Cu 375 sl (p < 0.05). Especially designed IUDs for nulliparous women had a better clinical profile compared with the standard IUD. This may improve the use of IUD in this population.