OBJECTIVE: To identify risk factors for injury to cricket fast bowlers using field-based tests. DESIGN: Prospective cohort study. SETTING: High performance Australian cricket. PARTICIPANTS: Ninety-one male adolescent and adult fast bowlers (aged 12-33 years). ASSESSMENT OF RISK FACTORS: A field-based pre-participation screening, consisting of musculoskeletal, fitness and anthropometric assessments and analysis of bowling technique was undertaken. Bowlers were prospectively monitored over the 2003-4 season and bowling workload and injuries were recorded. Logistic regression was used to identify injury risk factors. MAIN OUTCOME MEASUREMENT: Repetitive microtrauma injury to the trunk, back or lower limb associated with fast bowling. RESULTS: Two variables were identified as independent predictors of injury in the multivariate logistic regression analysis. Bowlers with hip internal rotation of < or =30 degrees on the leg ipsilateral to the bowling arm were at a significantly reduced risk of injury (OR 0.20, 95% CI 0.06 to 0.73) compared with bowlers with >40 degrees of rotation. Bowlers with an ankle dorsiflexion lunge of 12.1-14.0 cm on the leg contralateral to the bowling arm were at a significantly increased risk (OR 4.03, 95% CI 1.07 to 15.21) than bowlers with a lunge of >14 cm. Bowlers with a lunge of < or =12 cm were also at an increased risk, but not significantly so (OR 1.38, 95% CI 0.40 to 4.84). CONCLUSIONS: Biomechanical research is needed to investigate how these two intrinsic risk factors increase injury risk so that appropriate interventions can be developed.