Despite the focus on adolescents, most unintended pregnancies occur in adults. The objective of this study was to identify reasons why adult women have unprotected intercourse when they do not desire pregnancy. We held 4 focus groups to explore reasons for unprotected intercourse. Participants were adult women aged 18 to 39 who were unmarried, fertile, not currently pregnant, not desiring pregnancy, and who had recently had intercourse without using effective contraception. Sessions were audiotaped and transcripts were analyzed thematically. Women gave 146 reasons for unprotected intercourse. Four major categories emerged: method-related, user-related, partner-related, and cost/access-related reasons. The reasons for unprotected intercourse were numerous, but could be organized into a logical framework. The results suggest that multidimensional interventions may be needed to effectively reduce the rate of unintended pregnancy.