Abstract: Dominance hierarchies were studied in 11 herds of domestic horses and ponies (Equus caballus). A paired feeding test was utilized to establish the dominance--subordination relationship between each pair of animals in a herd. Aggressive actions, threats, bites, kicks and chases were also recorded. In small herds linear hierarchies were formed, but in large herds triangular relationships were observed. Aggression was correlated with dominance rank. Body weight, but not age, appear to affect rank in the equine hierarchy. Juvenile horses were more likely to share feed with each other than were adult horses and were usually subordinate to adult horses. The daughters of a dominant mare were dominant within their own herds.