Background: Unintended pregnancies are a major public health problem in the United States, and intrauterine devices (IUDs) are among the most effective reversible birth control methods available. Historically, there have been concerns about IUD use and infection among young and/or high-risk women that may increase the risk of pelvic inflammatory disease (PID) and subsequent infertility. Methods: The Contraceptive CHOICE Project (CHOICE) was a prospective cohort study of over 9,000 women 14-45 years of age residing in the St. Louis area who were interested in initiating a new form of reversible contraception. At enrollment, participants were counseled regarding long-acting contraceptive methods with the goal of increasing awareness of all reversible methods available. Participants were also tested for Neisseria gonorrhoeae (GC) and Chlamydia trachomatis (CT) during enrollment and were provided with contraception at no cost for 2-3 years. Results: We estimate the frequency of self-reported PID in new IUD users compared with women using other contraceptive methods. Among both new IUD users who tested positive for GC and/or CT and those who tested negative, the PID rate was 1% or below. Conclusions: Our results demonstrate that IUD use is safe for all women, including women at high risk for sexually transmitted infections.