BACKGROUND: Tobacco causes one in ten adult death worldwide, about 5.4 million death in 2006. The number of death will be doubled by 2020 if cigarette consumption habits continue. Tobacco is ranked in the world's major causes of death that can be prevented. Nine hundred million people (84%) world smokers in developing country. Indonesia is a country with the third largest cigarette consumer in the world after China and India. OBJECTIVE: Peer educators are established on student with enough knowledge in smoking effects, ability of communication techniques and assertive behavior with peers in changing smoking behavior to create free smoking area. METHOD: This study is a quasi experiment with one group with pre and post test desain. Subjects were 20 high school students SMA Tiga Maret (GAMA) Yogyakarta in March 2011. The sampling technique peer educators using simple random sampling by means of all classes represented at least 3 students, 20 students with same sex proportion. Subject of validity and reliability questionnaire were 126 SMA GAMA students. Instrument used questionnaire knowledge of smoking and questionnaire behavior intentions of peer educators. Intervention are given on lecture, group discussion, simulation, role play and training effective communication techniques of assertive behavior. Analysis of the data used is paired t-test. RESULT: There is an increase in the average value of peer educators behavior intention scores of 0.69 and significant difference (p = 0.003) between knowledge pre test and post test in group of peer educators. CONCLUSION: There is an increase in the value of the average scores of behavior intention peer educators and significant differences between the level of knowledge before and after the intervention program peer educators.