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Volume 29, Number 6, November/December 1997 tive pills (the first 21 of each 28-day cycle) without interruption. Oral contraceptive protection is expected to decrease when two or more consecutive hormonally active pills are skipped.3 It is not uncommon for prolonged intervals to occur between doses of self-administered medication.4 Between one-third and one-half of users of medications in pill form miss enough doses to place themselves at therapeutic risk at least occasionally.5 Self-reports have shown that 3–60% of oral contraceptive users, depending on the population studied, miss pills.6 An increased risk of unintended pregnancy has been documented among women who have reported missing pills,7 but this risk can be modified by two factors: the timing of coitus and the use of backup contraception. The instructions for correct oral contraceptive use that are included in all patient package inserts, which have the approval of the U. S. Food and Drug Administration, state that coitus should be avoided for the first seven days after initiating oral contraceptive use, whenever two or more consecutive active pills are missed and when the hormonefree week is extended by more than one day. They also state that if coitus occurs Deborah Oakley is professor at the Center for Nursing Research, University of Michigan School of Nursing, Ann Arbor. Linda Potter, visiting research collaborator at the Office of Population Research, Princeton University, was principal scientist at Family Health International (FHI), Research Triangle Park, NC, at the time this research was conducted. Emilita de Leon-Wong is senior biostatistician, and Cynthia Visness is research associate, FHI. This analysis was supported by a grant from the Henry J. Kaiser Family Foundation, Menlo Park, CA, and by inkind donations by Ortho-McNeil Pharmaceuticals, the university health services at the Universities of Michigan and North Carolina, Planned Parenthood Centers of West Michigan, and the Wake County, North Carolina, Health Department. Partial support for this work was also provided by FHI with funds from the U. S. Agency for International Development. The views expressed in this article do not necessarily reflect those of any of the supporting agencies. Oral Contraceptive Use and Protective Behavior After Missed Pills