Seven randomised controlled trials involving 1919 participants were included. Some trials were compromised by poor methodology, including lack of blinding and incomplete outcome data. Four trials, including 287 participants, examined interventions directly targeted at preventing hamstring injuries. Three of these trials, which tested hamstring strengthening protocols, had contradictory findings, with one small trial showing benefit, although the control rate of mainly minor hamstring injury was unusually high. The other two trials found no benefit, with a greater incidence of hamstring injury in the intervention group. One unpublished and underpowered trial provided some evidence that manual therapy may prevent lower limb muscle strain (RR 0.13, 95% CI 0.02 to 0.97), although the finding for hamstring injury did not reach statistical significance (RR 0.21, 95% CI 0.03 to 1.66). There is insufficient evidence from randomised controlled trials to draw conclusions on the effectiveness of interventions used to prevent hamstring injuries in people participating in football or other high-risk activities. The findings for manual therapy need confirmation.