Although ethograms of social play behaviour have been formulated (McDonnell & Poulin, 2002; Zharkikh, 2003) few studies focus on equine social play (Christensen et al., 2002). Social play studies have largely focussed on the time budgets and generalised interactions between herds (for example Boyd, 1988) rather than specific social behaviour sequences between limited numbers of horses. However, by observing pairs or small groups of animals, much may be learned about the dynamics of social communication in a particular species (Kalmus, 1969; Poole, 1972). Although play appears to be considered as either functionless or as serving different roles depending on species, age and even sex of individuals Burghardt (2006) speculated that 5 selected advantages in the performance of play within the behavioural repertoire of an animal existed, control, adaptive function, development, evolution and private experience. Further knowledge of equine social play may be of benefit to equine welfare and performance. The aim of the current study was to describe and quantify the involvement in social play and its initiation within an established group of young horses.