Purpose: This study examined the alterations in circulating creatine kinase (CK) levels, leukocyte trafficking, delayed onset muscle soreness (DOMS), muscle function in response to Gaelic football match-play in male adolescents. Methods: Participants (n=30, age 17.41 ± 0.78 yr, height 176.42 ± 7.13 cm, and mass 72.03 ± 6.49 kg) played a specially organised 15-a-side Gaelic Football game of 60 min duration. Blood samples were taken before the game, immediately post-game (Post), 12 h postgame (12 h), 36 h post game (36 h) and 60 h post game (60 h). Subjective muscle soreness, sprint performance and peak force were measured post, 12 h, 36 h and 60 h. Heart rate and movement patterns were continuously measured throughout the game using telemetry and GPS tracking, respectively. Heavy to severe impacts were classified as acceleration G-forces ³ 7 recorded via portable accelerometry. Results: Participants covered an average distance of 6.1 ± 1.1 km during match play. The majority (72%) of the distance involved walking and jogging and high speed and maximal activity accounted for 10% of the total distance. There was a total of 155 impacts ≥ 7 G-forces. C K levels were significantly higher than baseline immediately post-game and 12 h and returned to pregame values at 36 h. Compared to pre-match values circulating leukocytes and granulocytes were significantly higher than pre-game values immediately after the game and decreased significantly below pre-games values at 12h, 36 h and 60 h. Circulating lymphocyte numbers were significantly decreased below immediately post game and at 36 h post game. There was no change in the number of circulating monocytes. Compared to pre-game values, there was a significant decrease in peak force at 12 h and 60 h and a significant increase in 5 m and 20 m sprint times at 12 h, 36 h and 60 h. DOMS scores were significantly higher than pre-games values at 12 h and 36 h and lower (p<0.05) than pre-game values at 60 h. There was no significant relation between impacts and CK levels. Conclusion: Competitive Gaelic football match results in significant changes in CK levels, DOMS, leukocyte trafficking, peak force and 5 m and 20 m sprint performance.