In view of the developmental approach to sexual behavior, this article presents the stages of sexual behavior leading to coitus in four grades of high school students in Israel and the sociodemographic factors associated with initiating coitus. Analyses were based on data from the first national study dealing comprehensively with sexuality in 30 years. A self-administered questionnaire was completed by a random sample of 4,609 students of the General Educational (secular) system that included 68% of the Hebrew-speaking sector or 55% of all students in Israel. Our findings indicated a progressive set of stages of sexual behavior forming a Guttman scale, from kissing and petting over the clothes though petting under the clothes and genital touching to coitus. In comparison to results of a 1970 Israeli survey, we found an increase in practice in all Guttman scale stages of sexual behavior, as well as a diminished gap between genders. The gap fully disappeared in the three lower stages. Predictive variables of coitus initiation included gender, religiosity, immigration status, family structure, perceptions of academic achievements, and the proportion of peers practicing coitus. In addition to gender, perception of the proportion of peers that already practiced intercourse was the best predictor followed by grade, perception of academic achievement, and family structure. Marked differences were noticed between genders regarding associations with religiosity and immigration status. The discussion focused on comparisons to findings in other countries, the contribution of the findings to the understanding of Israeli adolescents' sexual behavior, and practical educational implications.