PURPOSE: This study was done to investigate the route of sexual knowledge acquisition and sexual problem behavior of primary school students in one province, North Cholla. METHOD: The participants in this research were 990 primary school 5 and 6 grade students chosen at random in big cities, small towns and rural areas of North Cholla Province. RESULTS: The routes for sexual knowledge acquisition were through classes and the teacher at school (40.6%), members of peer groups or seniors (26.1%), internet (15.3%), parents (10.0%), and multimedia (8.0%). The percentages for domains of sexual problem behavior were sexual impulse, 3.8%, sexual violence, 3.7%, masturbation, 2.7%, voyeurism, 1.8%, prostitution, 0.8%, transvestism, 0.5%, and exhibitionism, 0.1%. Sexual problem behavior experienced by 5.0% or more of the students was reported as the experience of another person compulsory touching their bodies, the desire to embrace and the desire to kiss a friend of the opposite sex. The biggest sexual problem behavior for the students was sexual violence and sexual impulses toward friends of the opposite sex. The experience rate for sixth graders was higher than for fifth graders (p<.05) and the experience rate of another person compulsory touching their bodies was higher for boys than for girls (p<.05). CONCLUSION: These findings suggest that systematic programs and curriculum should be developed for sexual problem behavior prevention.