Background: In children aged 4 to 8 years, booster seats are estimated to reduce by 59% the odds of sustaining clinically significant injuries during a motor vehicle crash, compared to using ordinary vehicle seat belts. Given the safety benefits of booster seats, public health and traffic safety agencies recommend their use for children aged 4 to 8 years traveling in motor vehicles, until the vehicle seat belt can fit them properly. Despite these benefits, booster seat use remains low. Interventions aimed at promoting the use of booster seats for children aged 4 to 8 years have been implemented, but there is little evidence regarding their effects. Methods: The Cochrane methodology was used to assess the effects of interventions to increase booster seat use for children aged 4 to 8 years. The reviewers searched online databases, scanned reference lists, hand-searched journals, and contacted relevant agencies and researchers for both randomized controlled trials and controlled before-and-after evaluation studies. The search concluded in 2005 and was not restricted by publication status or language. Results: The search yielded 1350 potential studies. Of these, five studies involving 3070 individuals met the inclusion criteria. Interventions were generally effective in increasing booster seat use among children aged 4 to 8 years. Education paired with incentive or distribution programs produced more consistent results than education-only interventions that targeted parents, children, or both. Conclusions: Incentives or the distribution of free booster seats combined with education increase the use of booster seats. © 2006 American Journal of Preventive Medicine.