Preschool-age children (range: 2.5-5 years old) were videotaped while in the sandbox and the climbing apparatus areas of a preschool playground prior to (i.e. baseline) and after a teacher "zone defence" training. The zone defence involved teachers being assigned to specific playground areas to monitor safety and facilitate the children's play and peer interactions. The pretest data revealed less complex play behaviours in the sandbox area (i.e. greater aimless behaviour and solitary play) compared to the climbing area, and greater onlooker behaviour in the climbing area than in the sandbox area. Pre-to-post zone defence revealed a decrease in teacher interaction with other adults and an increase in teacher-child interactions in the playground as well as overall decreases in children's play behaviours on the playground. Methods for coding and analysing group playground behaviours and the implications of teacher proximity in the playground are discussed. (Contains 1 note and 4 tables.)