The aims of the study were to (1) analyse the activity profile of youth football players during competitive matches, and (2) examine the relationship between physical match performance and intermittent exercise performance as well as VO2max. Thirty youth male football players, aged 14-17 years, carried out a laboratory treadmill test for determination of VO2max as well as the Yo-Yo intermittent recovery level 1 (Yo-Yo IR1) and Yo-Yo intermittent endurance level 2 (Yo-Yo IE2) tests. Time-motion analysis and heart rate (HR) recordings were performed during two competitive matches per player. Distance covered during the match was 6311 ± 948 (range: 4435-8098) m, of which 12% were high-intensity activities (HIA; 759 ± 437 [374-2062] m), and 5% was backwards running (309±205 [12-776] m). Mean match HR was 168 ± 12 (140-187) bpm, corresponding to 85% (69-91) of maximum HR. The total distance covered in the last 13.3-min period of the match was 40%, 26% and 17% lower than in the first, second and fourth 13.3-min periods of the match, respectively (P<0.05). The distance covered in backwards running decreased by 31% and 37% from the first to the last 13.3-min periods of the first and second half, respectively (P<0.05). The Yo-Yo IR1 was significantly associated with the time spent with sprinting during the match (r=0.63; P=0.002) and during the last 13.3-min period (r=0.63; P=0.022). Both Yo-Yo IR1 and Yo-Yo IE2 were correlated with the time spent with match HIA (r=0.56 and r=0.57, respectively; P<0.05). No significant relationship was observed between VO2max and match time-motion variables (r=-0.13-0.25; P>0.05) or Yo-Yo test performances (r=0.09-0.26; P>0.05). In conclusion, youth football players have a high heart-rate loading during match play and a decreased running performance towards the end of the game. The intermittent exercise capacity, as determined in the Yo-Yo IR1 test, appears to be a valid indicator of high-intensity exercise performance in youth matches.