RESUMEN
Summary: Sustainability of health promotion programs is essential to maintain their positive effects. However, few studies have examined the extent of program sustainability and the factors influencing it. We examined these issues through the Good Behaviour Game (GBG), a classroom-based program in primary schools with beneficial behavioural and health-related effects that was implemented in 2008. GBG coordinators of 17 participating schools were invited in the study 2 years after the initial program implementation. Sustainability was measured using a 20-item checklist comprised of four dimensions of routinization including: memory, adaptation, values and rules. A semi-structured interview was then completed with 16 of the GBG coordinators to discuss the checklist scores and to probe in more depth the current level of sustainability. Based on the checklist scores, sustainability of the GBG was considered 'high' in five schools, 'medium' in another five and 'weak' in six. Factors influencing sustainability identified by GBG coordinators were organizational strength, strong leadership, program championship and the perceived modifiability and effectiveness of the GBG. Also, different factors were related to different dimensions of routinization. The combination of a sustainability checklist and an interview about influential factors may help to further clarify the sustainability construct and reveal which implementation sites, routinization dimensions and influential factors should be explored to further facilitate the sustaining of programs with proven effectiveness.