Patient cost sharing for contraceptive prescriptions was eliminated for certain insurance plans as part of the Affordable Care Act. We examined the impact of this change on women's patterns of choosing prescription contraceptive methods. Using claims data for a sample of midwestern women ages 18-46 with employer-sponsored coverage, we examined the contraceptive choices made by women in employer groups whose coverage complied with the mandate, compared to the choices of women in groups whose coverage did not comply. We found that the reduction in cost sharing was associated with a 2.3-percentage-point increase in the choice of any prescription contraceptive, relative to the 30 percent rate of choosing prescription contraceptives before the change in cost sharing. A disproportionate share of this increase came from increased selection of long-term contraception methods. Thus, the removal of cost as a barrier seems to be an important factor in contraceptive choice, and our findings about long-term methods may have implications for rates of unintended pregnancy that require further study.