This study examines trends and differences in premarital sex prevalence from 1993 to 2003 among young women aged 15–24 in Kenya and the Philippines in relation to household and community membership. Using population-based DemographicandHealthSurveys from these two countries, multilevel logistic models were used to estimate the relationships between premarital sex, community-level factors, and individual/household backgrounds. The results show a significant decline in premarital sex prevalence in Kenya but a significant increase in this in the Philippines, although, overall, premarital sex is more prevalent in Kenya than in the Philippines. Multilevel analyses further found dramatic differences in premarital sex risks across household and community membership and countries. The large difference in premarital sex risks across these countries suggests that policies aimed at promoting reproductive and sexual health among young women should be context specific