The ability of young children to manage their emotions and behaviours is an important prerequisite for social adjustment and school readiness. With an increase in early-onset behavioural difficulties in children, understanding changes in child behaviour during the preschool years and the factors that influence it is a priority for policy and practice. Despite much evidence on the association between language and behavioural difficulties in children, few studies have examined longitudinally language and problem/prosocial behaviour in early years. Using a UK community-based sample, Dimitra Hartas, from the University of Warwick, examines the association between language, gender and behavioural, social and emotional difficulties and prosocial behaviour during the toddler years and at school entry. The findings showed a moderate decline in behavioural and social difficulties during preschool, and stability in emotional difficulties. Moderate associations were found between vocabulary and problem behaviour but not prosocial behaviour, with literacy-based language emerging as a substantive predictor of teacher-rated behaviour. These findings have important implications for early years provision.