This prospective cohort study examined the associations of shoulder dislocations, instability or rotator cuff injuries in collegiate rugby union players with potential risk factors recognized in preseason medical screening examinations. The study subjects were 69 elite rugby players from one university rugby club. Basic demographics, injury experience and current physical findings were assessed, and shoulder injuries sustained during 2 playing seasons were recorded. Risk factors for shoulder injuries were determined using a logistic regression model. Fifteen players sustained shoulder injuries during the 2 seasons. A history of injury (OR, 6.56; 95%CI, 2.04—20.98; p=0.00), a positive result in the load and shift (LAS) test (OR, 2.55; 95%CI, 0.92—7.06; p=0.07) and the internal/external rotational (IR/ER) muscle strength ratio (OR, 1.39; 95%CI, 1.08—1.77; p=0.00) were associated with shoulder injuries. A history of injury, a positive LAS test result, and the IR/ER muscle strength ratio are important risk factors for injury in collegiate rugby players.