Background Approximately 16% of all sports injuries in the Netherlands are the result of playing outdoor soccer. Objective The aim of this intervention study is to investigate the cost-effectiveness of an injury prevention program (‘The11’ from FIFA) in male amateur soccer players. The hypothesis is that the ‘The11’ exercises have a beneficial effect on injury incidence, injury severity, medical costs and/or absenteeism. Design The study is a two-armed cluster randomised controlled trial. Randomisation has taken place on a cluster level: the regional competitions. Setting First class amateur teams, in two separated districts in the Netherlands, participate in this study. All participating teams have practice sessions 2–3 times a week. Participants Male players aged 18–40 years were eligible for inclusion in the study. 22 teams participated in this study, resulting in 460 players performing an intake at the start of the intervention season (intervention group 214 players, control group 246 players). Intervention The teams in the intervention group were instructed to perform ‘The11’, during each practice session throughout the 2009–2010 season (September–June). All teams of the control group were asked to continue their practice sessions as usual. Main outcome measurements The primary outcomes of the study include injury incidence, healthcare use and absenteeism. These outcomes were registered online during the competitive season 2009–2010. Results Preliminary results show that the proportion of injured players was almost equal for both groups (58.9% vs 57.7%). The injury risk for both research groups was the same (0.92). The sports absenteeism was on average 1 day longer in the intervention group (30.3 vs 29.3 days). Conclusions First impression is that there are no significant differences between the two research groups. However, more extensive results of this study, particularly focused on possible confounders and cost-effectiveness, are expected in January 2011 and can be presented in Monaco.