The study found that standard Y-STR methods are insufficient to detect DNA from both the cervix and posterior formix at all post-coitus data collection times of 4,7,9, and baseline of 10 days; however, there was strong data that show using enhanced Y-STR enabled DNA identification from cervix and posterior formix through the first post-coitus menstruation. An association was found between diminished DNA recovery and menstruation and the use of hormonal birth control. Sixty-six of 112 consenting monogamous couples completed all phases of the study protocol. Eligible participants provided consents, eligibility data, and agreement to complete a diary during four 10-day abstinent periods, and collect post-coital samples at baseline and 4-,7- or 9-days. Upon protocol completion, participants mailed samples to the forensic laboratory for Y-STR methods analysis. Secure physical environments and blinding of laboratory personnel and statisticians to all participants information protected personal health information. 14 figures, 11 tables, 105 references, and a listing of dissemination publications and presentations