Objective: To identify risk factors for injury to cricket fastbowlers using field-based tests.Design: Prospective cohort study.Setting: High performance Australian cricket.Participants: Ninety-one male adolescent and adult fastbowlers (aged 12–33 years).Assessment of risk factors: A field-based preparticipation screening, consisting of musculoskeletal,fitness and anthropometric assessments and analysis ofbowling 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 microtraumainjury to the trunk, back or lower limb associated with fastbowling. Results: Two variables were identified as independentpredictors of injury in the multivariate logistic regressionanalysis. Bowlers with hip internal rotation of (30u onthe 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 .40u of rotation. Bowlers with an ankle dorsiflexion lunge of 12.1–14.0 cm on the leg contralateral to the bowling arm were at asignificantly 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 (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.