Purpose: The purpose of this study was to identify the effects of sex education using multimedia program on knowledge and attitude about sex. Method: The subjects of this study were 282 middle school boys in seoul. The data were collected from the 4th of Jun. to 30th of Jun. 2001. This program consisted of 6 subtopics and provided 3 sessions for each class. The per-test was given before the therapy to measure variables and the post-test was performed after intervention. The data were analyzed by the SAS program using t-test. Result: The results of this study are as follows. After intervention, the level of knowledge and attitude were increased significantly. Conclusion: The sex education using multimedia program is effective in helping middle school boys improve their healthy attitudes and thoughts toward sex.