Inter-team behaviour in elite-standard youth soccer during small-sided games. Soccer is a complex game with interacting players and teams. Team members cooperate to score a goal and opponent players try to keep the opponent from scoring. Tactical team behaviour seems to interact with the opponent team behaviour during small-sided games (SSGs). The aim of this study is to determine the inter-team behaviour in elite-standard youth soccer players of two age categories during SSGs. Differences were found for the lateral stretch index and the lpwratio between age groups, meaning that Under 19 made more use of the pitch width. In contrast, no differences existed in the coordination patterns between the teams. Both age groups were similarly attracted to a dominant in-phase behaviour and a less dominant anti-phase behaviour. These coordination patterns were determined for the total duration of SSGs. Future research should focus on the influence of ball possession and the transition of possession between teams on the dominance of coordination patterns.