OBJECTIVES: The prevalence of intrauterine device (IUD) use is low among women of reproductive age in the United States.  The objective of this study was to examine the trend in IUD insertions and related medical expenditures between 2002 and 2007 in a population of women covered by employer-sponsored health insurance (ESI). METHODS: We conducted a population-based study using the MarketScan Commercial Claims and Encounter Enrolled Population database.  We identified women, 15-49 years old who filed a claim for the insertion of an IUD or IUS (the Levonorgestrel-releasing IUD) between January 1, 2002 and December 31, 2007.  We adopted the MarketScan national weights in order to generate nationally representative estimates. RESULTS: The number of new IUD/IUS patients in the ESI-covered population doubled, from 70,851 (2/1,000 eligible women) in 2002 to 154,366 (8/1,000) in 2007. Meanwhile, the market share of the IUS increased from 35% to 80% of all IUD insertions. The mean copayment for IUD (IUS) devices decreased from $13.0 ($14.6) in 2002 to $3.5 ($3.6) in 2007 after adjusting for inflation (in 2007 dollars), and the percent of patients with zero copayment for the device and for the insertion procedure increased from 65% to more than 80% and form 58% to 73%, respectively. The average net reimbursement for the IUD increased 17.5% between 2002 and 2007, from $311.92 to $366.64, while that for the IUS increased 7.5%, from $405.36 to $435.49. CONCLUSIONS: The increase in medical expenditures associated with IUD/IUS insertions from 2002 to 2007 was driven by the growth in IUS insertions. IUDs have lower contraceptive failure rates than other reversible contraceptive methods, and higher rates of IUD use should lead to fewer unwanted pregnancies. Additional research is needed to understand whether the recent growth in IUS insertions is related to changing provider attitudes and more favorable insurance coverage.