Time-budgets of adult and weaned sub-adult horses were studied in a small population of Camargue horses living in semi-liberty. The categories of activities used were: Standing resting, Lying flat, Lying up, Standing alert, Walking, Trotting, Galloping, Rolling and Foraging. The main differences in time-budgets were related to age and to sex : young horses spent more time lying (sleeping), males spent more time standing alert and in rapid movements (trot, gallop), while usually foraging less than did the adult females. During the three years of the study the population increased from 20 to 54 horses and there were considerable changes in social structure as the number of adult males increased. Associated with these developments there were some changes between years in the time-budgets: the most striking of which was a general trend for all horses to spend less time lying. Nonetheless the time-budgets showed a considerable constancy across years and age/sex-classes, especially with regard to time spent foraging. This conclusion may provide a clue as to why horses have an unusual social system based on long term relationships between a male and the females of his harem.