This study examines the effects of a systematically designed innovation strategy on teachers' implementation of a sex education curriculum and its related determinants. A quasi-experimental group design was used to assess the effectiveness of the innovation strategy. Teachers filled in questionnaires on the determinants of curriculum implementation and kept a record of their actual use of the curriculum. We measured several determinants, including teachers' curriculum-related beliefs, characteristics of the interactive context and characteristics of the innovation strategy. Participating teachers ( n = 109) carried out most of the activities they were supposed to (81%). Multiple linear regression indicated that their outcome beliefs and perceived instrumentality of the curriculum best predicted extent of use of the curriculum ( R 2 = 0.23). The innovation strategy had a positive impact not only on extent of use (18.4 activities versus 15.8 activities; t = 2.3, P < 0.05), but also on teachers' curriculum-related beliefs. It can be concluded that a systematically designed innovation strategy has the potential to produce significant changes in classroom-based sex-education practices. Not only did teachers exposed to the innovation strategy implement more of the curriculum than teachers in the control group, also teachers' beliefs and expectations about student learning constituting their classroom behavior changed accordingly.