Objectives: This is an explanatory correlational study to assess the level of and the relationship of the related factors of health promotion behavior by gender among college students. Methods: Subjects were 950 of the freshmen of the year 2010 at a university in a city adjacent to a metropolis, in S. Korea. Data were collected from the freshmen who understood the purpose of the study and agreed to participate during a freshmen core course using a structured questionnaire. Related factors include active- and passive-self efficacy, internal health locus of control, and social support. Related factors were compared between male and female using t-test and the relationship between the related factors and the health promotion behavior was analyzed separately for each sex, by multiple regression analysis using SPSS 12.0. Results: There were differences in the related factors of BMI between male and female students. They were alcohol behavior and perceived health status among female students while smoking status, alcohol behavior, perceived health status, and BMI among male students. Result from the multiple regression analysis revealed difference in the related factors and in the magnitude of the relationship evaluated by the standardized beta coefficients. Significant factors, listed by the magnitude of beta coefficients, among female were social support, active self efficacy, passive self efficacy, internal health locus of control, and alcohol behavior. Significant factors among male students were social support, active self efficacy, smoking, internal health locus of control, passive self efficacy, and perceived health status. Conclusions: There are gender difference in health promotion behavior and the related factors. The results suggest that the gender differences need to be considered when planning health promotion programs in college. Further research is necessary in order to draw consensus on roles of the related factors of health promotion behavior.