Objective: To assess and evaluate the injury risk associated with the scrum in English professional rugby union in the 2011-2012 season. Design: Prospective, cohort. Participants: Players at English Premiership rugby union clubs. Outcome measures: Frequency of team scrum-events per match; incidence (injuries per 1000 player-hours; propensity (injuries/1000 events); risk (days absence per 1000 player-hours and days absence per 1000 events). Results: 31% of scrums in competitive matches resulted in collapse. Injury incidence associated with collapsed scrum-events (incidence: 8.6 injuries/1000 scrum-events) was significantly higher than those scrums that did not collapse (incidence: 4.1/1000 scrum-events). Conclusions: The injury risk associated with collapsed scrum supports the continued focus on reducing scrum collapse through changes in, and strict application of, the laws surrounding the scrum.