The 20-m shuttle run (20-mSRT) is a widely used field test to estimate peak oxygen consumption (VO2peak) and thus to assess aerobic fitness of adolescents (11). The purpose of this study was to analyse differences in basic anthropometric measurements (stature, body mass, percent body fat, BMI) and in aerobic fitness of Hungarian and Ukrainian adolescent boys and girls. We examined gender differences in maximal speed (km h-1), in peak VO2 (mL kg-1 min-1) and maximal heart rate (HRmax min-1). Two hundred ninety-two Ukrainian (mean age=16.5±0.5) and 374 (mean age=16.5±0.5) Hungarian adolescents volunteered to participate in this study. Differences were analysed using factorial analysis of the variance (ANOVA) and Student's t-test. Statistical significance was set at p