en 23926523 Background: This paper aims to examine the reproductive health and behaviors which might expose young people at risks of STIs/HIV and potential correlates of such behaviors among female college students in Tehran. Methods: This paper focuses on the study conducted on a sample of 1743 female undergraduate students in four multidisciplinary universities in Tehran during 2005-2006 using a two-stage stratified cluster sampling. The main focus was to determine the predictors of premarital heterosexual reproductive behavior among female students. Results: The mean age of the unmarried students was 21.4 years. Low self-efficacy (OR=7.87, p <0.001), perceived peers' liberal attitude on virginity (OR= 4.33), perception of parents' liberal attitude towards relationship with the opposite sex and poor family atmosphere (OR=3.04 and 2.20, p <0.001, respectively) were predictors of ever having any type of sexual experience after controlling for other factors. The only predictors of penetrative sex remained in the logistic model were older age (OR=5.95), low self-efficacy (OR=10.86), poor family atmosphere (OR= 2.96), liberal parental attitude (OR=4.29) and liberal peer norms on virginity (OR= 4.90). Conclusion: Interventional programs need to be designed at various levels such as enhancing self-efficacy, informing families of the protective role of a balanced control and monitoring over adolescents' behavior and choices of peer network against premarital sexual activity. Determinants, HIV/STI, Reproductive behavior, Risk taking behaviours, Young people 39 52 https://www.jri.ir/article/484 https://www.jri.ir/documents/fullpaper/en/484.pdf FaridehKhalajabadi FarahaniMidwifery and Reproductive Health Department, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran147JohnClelandDepartment of Epidemiology and Population Health, Centre for Population Studies, London School of Hygiene and Tropical Medicine, London, EnglandJohnCleland991Amir HooshangMehryarDepartment of Behavioural Science, Institute for Research on Managment and Planning, Tehran, IranAmir HooshangMehryar992