As we know that one of the world serious health problem is AIDS. In Thailand, statistics revealed that Ranong is the province having the highest HIV infected rate. The majority of those infected are age 15-19. Therefore, the health education program emphasising the reinforcing behavior change process through the action research design was implemented. As the result, the action research integrated with the problem-based learning principles and social learning theory was done to change knowledge,attitude, and practice among teenagers. One hundred seventy-seven first year technical students were selected purposively as sample of this study. Out of 177, only 44 students reported having had sex experience. Interview technique, self-administration questionnaire, observation technique, and health record review were employyed for data collection of knowledge, attitude and practice on AIDS. The study was conducted during October, 1990 to February 1991. Descriptive statistics, Paired Samples t-test and Pearsons Product Moment Correlation were used for data analysis. The statistically significant level 0.05 are considered in this study. The findings revealed that the problem-based learning helps increased students analysing skill which leads to effective knowledge and attitude change. In addition, the self control ability through the group counselling was also contributed to the change. To illustrate, 11 percents increased of those students who had experience avoided or abstained having sex with prostitutes but the rate of condom use has increased up to 60 percents. For those who had no sex experience reported the increased ability of avoiding sexual arousal activities and of controlling their sexual needs. The technical college administrators need to focus on this latter group not only because they are the majority but also because they are at risk with the casier tendency to motivate for preventive action than those with sexual experience.