OBJECTIVES: To evaluate the cost effectiveness of a proprioceptive balance board training programme for the prevention of ankle sprains in volleyball. METHODS: A total of 116 volleyball teams participated in this study which was carried out during the 2001-2002 volleyball season. Teams were randomly allotted to an intervention group (66 teams, 628 players) or a control group (52 teams, 494 players). Intervention teams followed a prescribed balance board training programme as part of their warm up. Control teams followed their normal training routine. An ankle sprain was recorded if it occurred as a result of volleyball and caused the subject to stop volleyball activity. The injured player completed a cost diary for the duration of the ankle sprain. Analyses were performed according to the intention to treat principle. Mean direct, indirect, and total costs were calculated and were compared between the two groups. RESULTS: The total costs per player (including the intervention material) were significantly higher in the intervention group (36.99 (93.87)) than in the control group (18.94 (147.09)). The cost of preventing one ankle sprain was approximately 444.03. Sensitivity analysis showed that a proprioceptive balance board training programme aimed only at players with previous ankle sprains could be cost effective over a longer period of time. CONCLUSIONS: Positive effects of the balance board programme could only be achieved at certain costs. However, if broadly implemented, costs associated with the balance board programme would probably be lower.