In the United States, the rates of unplanned pregnancies and sexually transmitted diseases, including HIV infection, caused by unprotected sex is alarmingly high. Adverse outcomes of unprotected sexual intercourse continue to be a burden, not only for affected adolescents but for the community at large. Using data from the National Longitudinal Study of Adolescent Health, this study applied the PRECEDE model as a means to identify those salient risk factors and risk conditions of sex initiation and engagement in unprotected sex among adolescent students. Results showed that 52.6% of the students have had sexual intercourse and 54.5% of sexually experienced students reported inconsistent condom use during sexual intercourse. Logistic regression analysis showed that risks factors for having had sexual intercourse differ from those for having engaged in unprotected sex in sexually experienced students. Furthermore, these factors also differed between male and female students. Only students’ age and perceived hardships related to pregnancy were found to be common risk factors for both outcomes in both sex groups. Results suggest that the PRECEDE is a practical tool to aid program planners identify the intervention priorities most relevant to their target populations.