Purpose: For the survey of sexual behavior and activity in single male population, we examined the experience of masturbation, sexual intercourse and present sexual partner among? military soldiers. Materials and Methods: 830 military soldiers reported on sexual activity questionnaires and were taken physical examinations for evaluation of external genitalia. Results: The group who experienced sexual intercourse was 562(67.7%) and the other group who have not experienced was 268(32.3%). Among the former group, first subgroup who experienced first sexual intercourse with their lover was 452(80.4%) and second subgroup who experienced first sexual intercourse with prostitutes was 110(19.6%). The percentage of men who reported that they had experienced masturbation was 98.1%(815/830). Masturbation frequency was 2.6 times per month in the group without experience of sexual intercourse.? That of first subgroup was 3.5 times, and the second subgroup was 3.0 times per month. Those who experienced sexually transmitted disease were 40, which was 4.8% of those who experienced sexual intercourse. Conclusions: More than two thirds of adolescents experiences sexual intercourse and 5% experiences sexually transmitted disease at the end of adolescence, which reflects they are sexually active. We find out that the experience of masturbation is more in the military soldiers group than other groups reported and the reported frequency is significantly different among the groups with or without experience of sexual intercourse. Because any deviation or wrong concept in sexuality may cause many social and medical problems such as sexually transmitted disease or harmful genitalial lesions in our country, the sound sexual education should be the ground of our improvement of sexual concept.