This article examines the influence of sex education on sexual and reproductive behavior in Mexican women. Exposure to in-school sex education is identified and durationhazard models are estimated to assess its effects on initiation of sexual activity and use of contraception methods, and timing of first and second pregnancies. Results consistently reveal that women exposed to sex education begin using contraception methods earlier. Most evidence indicates that exposed women initiate sexual activity earlier. Findings suggest that timing of first pregnancy is not affected and that second pregnancy is postponed. Overall, outcomes from this study support the idea that sex education contributes to promote preventive sexual health.