Cervical dilatation is occasionally performed to facilitate IUD insertions in difficult-to-insert cases. Patient characteristics associated with the need for dilation and whether dilation is associated with an increased risk of early expulsion of the IUD have rarely been studied. This analysis, using the extensive international IUD data base developed and maintained by Family Health International, is intended to answer these questions. This case-control analysis revealed that nulliparous women as well as women who had used oral contraceptives or an IUD in the previous month were more likely to require cervical dilatation at IUD insertion. Breastfeeding women, on the other hand, were less likely to require cervical dilatation to facilitate IUD insertion. Hypotheses are generated from this analysis that need to be tested in future studies. The six- and 12-month gross cumulative life-table expulsion rates and other pertinent termination event rates (e.g., accidental pregnancies and removals due to bleeding and pain) were not found to be higher for women with cervical dilatation than for women without.