Objectives In a seven-year follow-up study, the author and colleagues examined the development of social skills from childhood to late adolescence, with a particular focus on aggressive behaviour. This paper presents a review of the most important findings of the project. Results and conclusions Social strategies explained aggressive behaviour, and changes of strategies predicted changes of behaviour. Aggressive behaviour was, however, very stable, and spontaneous change from an aggressive child to a sociable adolescent was not observed. This emphasizes an importance of early prevention of aggression. Disagreement between the children's and their parents' problem-solving strategies was apparent, suggesting that interventions to reduce a