Abstract: Results from studies on the social behaviour of the Icelandic horse kept in different types of groups will be presented. Most groups were studied for more than 75 hours. The groups vary in composition and in stability. Some groups include stallions (6 groups) while others breeding mares and foals (1), geldings, mares, sub-adults and foals (3), geldings, sub-adults and mares (2), geldings and mares (4), one-sex 1year olds (3) and sub-adults (1). In some of the groups the residency of individual horses was similar (stable groups) while in others the composition changed frequently or unfamiliar horses were all put together at the same time. The results show that both negative and positive interactions are more frequent in unstable groups. Also, interesting differences emerged when different group types were compared. The results are important for management and will be discussed in that context. KW -