Background The objectives of the study were to determine the most common injuries in Gaelic football and hurling and to quantify contributory factors. Hypothesis: The hypothesis tested was "Ankle sprains are a common injury in Gaelic football and hurling and their incidence can he linked to physical characteristics of the players", Methods. Experimental design: prospective study over four pears, Subjects: eighty male players of Gaelic football, and hurling, aged 18-27 Sears. Measures: the injuries sustained over a four-year period, physical fitness tests and examination at the start of the study which included assessment of: anthropometric variables, lower-limb proprioception, lung function, six aspects of flexibility, 15 aspects of posture and body mechanics. Results. 962 significant sports injuries which included: 218 strains and 184 sprains. 122 were ankle sprains; 79 to the left ankle and 43 to the right. 104 ankle sprains represented a recurrence of this injury in a particular individual, In 26 out of 34 of these subjects both ankles were involved. This suggests that recurrence is not primarily due to previous injury but to intrinsic factors in the subjects that predispose them to ankle sprain. The subjects who sustained ankle sprains had (1) greater height, (2) lower body mass index (3) a higher incidence of posture defects of the ankle and knee, (4) more clinical defects (5) a higher incidence of defective lower-limb proprioception, Conclusions. Ankle sprains are a common injury. Their incidence is linked to the five intrinsic factors listed above.