This study investigated the effect of repeated bouts of short-term, high-intensity cycling exercise on the salivary cortisol, testosterone and immunoglobulin (A) concentrations of 15–16 year old boys. Seventeen apparently healthy schoolchildren (aged 15.5 ± 0.4 years) participated in this study. All participants completed 6 × 8 s sprints, interspersed with 30 s recovery intervals on a cycle ergometer. Using the passive drool method, salivary samples were taken before, and 5 min after, exercise. The group mean for peak power output was 723.1 ± 180.3 s. There were significant changes (p ≤ 0.05) in both SalT and SalC, 5 min after completing 6 × 8 s cycle sprints. No significant differences (p > 0.05) were recorded for SIg(A). The increases in SalT and SalC reported in this study confirm that repeated bouts of short-term, high-intensity exercise produces significant physiological hormonal responses in adolescent boys, but does not affect mucosal immune function.