Purpose. We investigated the effects of a two-week high-intensity interval training (HIT) on cognition in adolescents. Methods. The participants were recruited from local high schools with an electronic messaging system. The HIT group participated in 4 high-intensity interval running sessions and 2 circuit training sessions. The control group (CG) continued their usual habits. reaction time, choose reaction time, working memory, visual memory, and learning were assessed by computerized CogState test battery. The intervention effect was investigated with repeated measures ANOVA and the effect size by Morris dppc2.Results. The total of 25 participants aged 17-20 years participated in the baseline measurements and were randomized into the intervention (n = 12) and control (n = 13) groups; 9 people in the HIT group and 10 in the CG also participated in the follow-up Citation: Stenman M, Pesola AJ, Laukkanen A. Haapala EA. Effects of two-week high-intensity interval training on cognition in adolescents -a randomized controlled pilot study.