The primary goal of this research was to use an experimental, observational method to study the development of anger expression during middle childhood. Eight-, 10-, and 12-year-old girls and boys (N = 382) were observed during a laboratory play session that was provoking in two ways: Participants lost a computer game they were playing for a desirable prize, and their play partner was a same-age, same-gender confederate actor who taunted them. Children's responses to the provoking play sessions--facial expressions, verbalizations, and gestures--were reliably coded. Overall, children in these age groups maintained a remarkable degree of composure. Girls made fewer negative comments than boys did, and fewer negative gestures. Older children maintained more neutral facial expressions, made fewer gestures, and were more likely to remain silent when provoked. When they spoke, older children made fewer negative comments, fewer remarks about the game, and fewer positive comments about themselves or the actor.