In 1998, a new organ donor registration system was implemented in the Netherlands to increase the number of potential donors. A high school education program was developed to prepare adolescents to make an informed decision about organ donation. A post-test only randomised controlled trial was conducted in 39 high schools including 2868 students. Students within schools were randomly allocated to either attend the organ donation education program or not. The impact of the program on students' intention to register their organ donation preference (and determinants thereof) were analysed using multivariate multileveling modelling (MlwiN). The results show that students who were exposed to the education program had more favourable registration intentions (B=.40), were more often willing to be donors (OR=1.45), and had greater knowledge about (B=3.84) and more positive social outcome expectations (B=.09) and self-efficacy regarding organ donation registration (B=.22). Lastly, they experienced significantly less negative outcome expectations related to organ donation registration (B=-.15). Students' evaluation of the school-based education program was favourable. The present organ donation registration program proved to be effective in changing determinants of organ donation registration, and a large-scale implementation in the Dutch high school curriculum is planned.