Numerous studies have reported IUD-related events in evaluating the rates of pregnancy, expulsion, and removal for bleeding and pain, but the inability to successfully insert an IUD has been overlooked. This study analyzed data on 51 unsuccessful insertions from 22 international centers collected on standard forms. The incidence of insertion failures was estimated to be between 2.3 and 8.3/1000 attempted insertions. No statistically significant risk factors in patient characteristics were delineated through a case-control analysis. The incidence of insertion failures among postpartum cases was highest for the Delta Loop (16.8/1000 insertions). Data suggest that failure to successfully insert an IUD may not be directly attributable to any specific host characteristic but rather is contingent on agent (IUD type) and provider (inserter) factors.