Objective. The aims of the study were to evaluate the long-term effects of a home-based smoking prevention program 'Smoke-free Kids' during preadolescence on smoking initiation during adolescence and to test the potential moderating role of parental smoking, socioeconomic status, and asthma. Method. In 2008,1478 9-11 year old children and their mothers were recruited from 418 elementary schools in the Netherlands. An independent statistician randomly allocated schools to one of the two conditions using a 1:1 ratio (single blind): 728 children in the intervention and 750 in the control condition. The intervention condition received five activity modules, including a communication sheet for mothers, by mail at four-week intervals and one booster module one year after baseline. The control condition received a fact-based intervention only. Intention-to-treat analysis was performed on 1398 non-smoking children at baseline. Results. In the intervention 10.8% of the children started smoking compared to 12% in the control condition. This difference was non-significant (odds ratio = 0.90,95% confidence interval = 0.63-1.27). No moderating effects were found. Conclusion. No effects on smoking initiation after 36 months were found. Perhaps, the program was implemented with children that were too young. Programs closer to the age of smoking onset should be tested.