Purpose: A prospective observational study design was used to assess selected fitness parameters in club level (CL) and county level (CO) Gaelic football players and, to determine the accuracy of the 20 m shuttle run test (20 MST) in predicting V 0 2max in Gaelic football players. Methods: A total of 213 Gaelic football players (95 CL, 118 CO) were recruited to part in the study Subjects underwent a number of laboratory and field-based tests to assess physical characteristics, flexibility, power, speed, agility and aerobic capacity. The validity and reliability of the 20 MST as a predictor of V0 2max was assessed on a random sample of 32 players representing CO and CL Each player undertook in random order 2 separate 20 MST tests and, 2 continuous incremental treadmill exercise tests to assess maximal aerobic capacity. Results CO had higher (p<0 05) levels of flexibility, lower (p<0 05) percent body fat and smaller (p<0 01) waist circumference than CL. There was no difference in any of the other measured physical characteristics between CO and CL County level players outperformed club players in all indices of speed and agility evaluated Vertical jump scores, anaerobic power, anaerobic capacity, V 0 2max , maximal heart rate or maximal ventilation and %V 0 2 at ventilatory threshold were similar in CO and CL. There was a significant positive relation (r =0 654, p<0 01) between the number of shuttle runs completed during the MST and measured V 0 2max, and between the estimated V o 2max and directly measured V 0 2max (r = 0 673, p< 0 01). Conclusion Physical characteristics are similar in CO and CL. With the exception of indices of speed and agility, fitness levels are similar in CO and CL. The 20 MST is a modest predictor of V0 2max in CO and CL.