This article addresses the effect of communicative activity on the use of language and gesture by school-age children. The present study examined oral narratives and explanations produced by children aged six and ten years on the basis of several linguistic and gestural measures. Results showed that age affects both gestural and linguistic behaviour, supporting previous findings that multimodal discourse continues to develop during the school-age years. The task (narration vs. explanation) also had clear effects on the use of language and gesture: gestures and subordinate markers were more frequent in explanations than in narratives, whereas cohesion markers were more often used in narratives. Altogether, these results show partly distinctive developmental patterns between narrative monologic discourse behaviour and explanatory behaviour in the context of dialogue and question-answer exchanges.