Recently the rate of adolescent smoking in Korea has increased rapidly, and various health problems related to smoking can be expected to increase in the future. Studies on smoking behavior report that assertiveness is important factor influencing on the adolescent smoking. PURPOSE: This study was conducted to develope a educational video for the purpose of adolescent's smoking prevention. METHOD: The 533 participating subjects, 269 in experimental group and 264 control group, in the study were 7th grade students. The content of video introduces three smoke tempting situations. The experimental group received 17 minute video education, and the control group did not receive any treatments. RESULT: The results show that the student's assertiveness was increased significantly in the experimental group after the video education. Student's attitude on smoking became more negative in the experimental group. However, in the control group, the intention, assertiveness, attitude was not changed. CONCLUSION: This assertiveness video can be useful educational resource for the smoking prevention program for adolescents. Also further study on longitudinal effect and application on drinking, drug abuse are needed.