Badminton-specific speed and endurance performance was evaluated in both cross-sectional and longitudinal studies of elite youth players and compared to the physiological capacities of world top-50 singles players.The cross-sectional study involved ten males in the category U15 (<15 years), ten U17, nine U19 and four senior elite players. They performed 30-m sprint, counter-movement jump (CMJ) and badminton-specific speed (B-SPEED) and endurance (B-ENDURANCE) tests. The longitudinal data were collected for ten U15 players with 1- and 2-year follow-up measures.Compared to seniors, B-SPEED performance was 20±5 % slower for U15 (P<0.001), 7±3 % slower for U17 (P<0.05) and non-significantly slower (3±3 %; P=0.27) for U19. B-ENDURANCE performance was 45±11 % shorter for U15 (P<0.001), 25±7 % shorter for U17 (P<0.001), and 17±10 % shorter for U19 (P<0.01). The longitudinal data for U15 revealed that B-SPEED performance improved from a 19±5 % (P<0.001) deficit at baseline to 5±5 % (P=0.23), at first-year and 2±3 % (P=0.43), at second-year follow-up. B-ENDURANCE performance improved from a 43±11 % deficit at baseline to 27±10 % and 17±7% at 1- and 2-year follow-up (P<0.001). CMJ also improved with ageing from 29±5 % deficit for U15 to 13±6 % deficit for U19 (P<0.01). In conclusion, badminton-specific speed improves markedly with ageing in youth elite players to achieve, by age 19, values matching world-class players. Endurance improved markedly, but with a significant deficit remaining in comparison to senior elite players.