The current study examined the effect of sprint interval exercise on postexercise oxygen consumption, respiratory-exchange ratio (RER), substrate oxidation, and blood pressure in adolescents. Participants were 10 normal-weight healthy youth (7 female), age 15-18 years. After overnight fasts, each participant undertook 2 trials in a random balanced order: (a) two 30-s bouts of sprint interval exercise on a cycle ergometer and (b) rested in the laboratory for an equivalent period. Time-matched measurements of oxygen consumption, RER, and blood pressure were made 90 min into recovery, and substrate oxidation were calculated over the time period. Total postexercise oxygen uptake was significantly higher in the exercise than control trial over the 90 min (mean [SD]: control 20.0 [6.0] L, exercise 24.8 [9.8] L; p=.030). After exercise, RER was elevated above control but then fell rapidly and was lower than control 30-60 min postexercise, and fat oxidation was significantly higher in the exercise than control trial 45-60 min postexercise. However, total fat oxidation did not differ between trials (control 4.5 [2.5] g, exercise 5.4 [2.7] g; p=.247). Post hoc tests revealed that systolic blood pressure was significantly lower than in control at 90 min postexercise (control 104  mm Hg, exercise 99  mm Hg; p<.05). These data indicate that acute sprint interval exercise leads to short-term increases in oxygen uptake and reduced blood pressure in youth. The authors suggest that health outcomes in response to sprint interval training be examined in children.