Evidence with regard to the incidence of injury to forwards and backs in the game of rugby league is extremely limited. A four year prospective study of all the injuries from one professional Rugby League club was conducted. All injuries that were received during match play were recorded, and those for forwards and backs compared. Forwards had a higher overall rates of injury than backs (139.4 [124.2-154.6] vs. 92.7 [80.9-104.6] per 1000 player hours, P < 0.00006). Forwards had a higher rate of injuries to all body sites with the exception of the ankle and the 'others' category of injury. They had significantly higher rates for the arm (11.6 [6.9-16.3] vs. 3.9 [1.4-6.4] per 1000 player hours, P = 0.005) and, the head and neck (53.9 [43.9-63.8] vs. 25.0 [18.7-31.4] injuries per 1000 player hours, P < 0.00006). Forwards had significantly more injuries than backs for contusions (17.1 vs. 7.3 per 1000 player hours, z = 2.85, P = 0.0044), lacerations (26.7 vs. 13.8 per 1000 player hours, z = 2.92, P = 0.0035) and haematomas (20.6 vs. 11.6 per 1000 player hours, z = 2.29, P = 0.02). Forwards were also more likely to be injured when in possession of the ball (70.5 [59.2-81.7] vs. 38.0 [30.2-45.7]), and also when tackling (33.2 [25.3-41.1] vs. 16.8 [11.6-22.1]). The higher rates of injury experienced by forwards were most likely as a result of their greater physical involvement in the game, both in attack and in defence.