Background Some sports, such as football, have a high incidence of hamstring injuries. Various interventions targeting the prevention of such injuries are in common use. Objectives To assess the effects (primarily, on the incidence of hamstring injuries) of interventions used for preventing hamstring injuries in physically active individuals. Search Strategy We searched the Cochrane Bone, Joint and Muscle Trauma Group Specialised Register (to December 2008), the Cochrane Central Register of Controlled Trials (The Cochrane Library, 2008, Issue 4), MEDLINE and other databases (to December 2008), reference lists and clinical trials registers. Selection criteria Randomised or quasi-randomised trials of interventions for preventing hamstring injuries were included; as were trials testing interventions for the prevention of lower-limb injuries, provided that hamstring injuries were reported. Secondary outcomes included compliance, severity and the occurrence of other leg injuries. Data Collection and Analysis Two authors independently screened search results, assessed methodological quality and extracted data. Risk ratios (RR) and 95% confidence intervals (95% CI) were calculated for dichotomous variables and are reported for individual and pooled data. Main Results Seven randomised controlled trials involving 1919 participants were included. All trials involved people, predominantly young adults, participating in regular sporting activities. 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 One unpublished and underpowered trial provided some evidence that manual therapy may prevent lower-limb muscle strain (RR 0.13, 95% CI 0.02 to 0.97), although the finding for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).Three trials testing interventions for preventing lower limb injuries for which data for hamstring injury were available found no statistically significant effect for hamstring injury for either proprioceptive protocols (two cluster randomised trials) or a warm up/cool down and stretching protocol (one trial). Authors' Conclusions 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 for these injuries. The findings for manual therapy need confirmation.