PURPOSE: This study was designed to identify the variables affecting male adolescents' sexual intercourse through a comprehensive analysis of individual and environmental factors. METHOD: The subjects of this descriptive survey on causal relations were 462 subjects enrolled in liberal and vocational high schools selected on a convenience sampling basis. The data collected from May-July 2002 was put to logistic regression analysis to build a forecast model. Findings: 1) Individual factors such as school record, experience seeking, non-inhibition and sexual permissiveness, 2) family factors such as parental living arrangement, 3) school factorssuch as career tract and 4) peer factors such as having a boy/girl friend were identified as significant variables forecasting sexual intercourse. CONCLUSION AND RECOMMENDATION: The theoretical model built on the basis of the major findings of this study will hopefully help promote a wholesome youth culture related to sexual intercourse.It is recommended that a program be developed that can help control the variables identified in this study along with a follow-up study to verify the model.