The aggression and spacing amongst light horse mares and their foals was examined while they were out at pasture. The mare-foal pairs were observed for approximately seven hours each day. The observations began when the foal was two months old and ended when the foals were approximately four months old. Observations of the foals continued until they were six months old. All occurrences of aggressive behaviour were recorded, along with the identity of those that were involved in the encounter. Aggression was also observed when the horses were fed supplemental grain. There were significant correlations between the rank of the mare with the rank of the foal (before and after weaning). There was also a significant correlation between rank and birth order, but this was only evident before weaning. The social relationships of the foals, along with their rank was not linked to their gender. The foals preferred to associate with the foals of the mares that their mother preferred to associate with both before and after weaning. As mares and foals increased in rank, so did the rate at which they would engage in aggressive encounters with other horses in the herd.