The aims of this research were to investigate the development of object manipulation and play in domestic horse foals, in order to gain a better understanding of its ontogeny. Also to investigate which sensory characteristics of objects elicit object manipulation and play in juvenile and adult domestic horses. Three groups of foals, one of a variety of breeds maintained in differing management regimens and two of Arabians maintained in similar management regimens, were studied. These groups were studied to determine whether any pattern could be detected in the development of object manipulation and play and what factors could affect this pattern. To ensure that all the foals had the opportunity to manipulate an object a Jolly Ball (Horseman's Pride, Ravenna, OH, USA) was placed in the field/stable during each observation. Object manipulation and play was observed throughout the first three months of life, suggesting that it is an important component of foals' behavioural repertoire for acquiring information about their environment and handling skills. Object manipulation and play did not appear to follow a definite pattern of progressive development during the first three months of life. It is likely that the development of object manipulation and play is different in each individual and is affected by factors including: breed, management factors, personality (boldness), social environment and experience. Bolder foals were more willing to investigate objects than more timid foals and socially isolated foals displayed more object manipulation and play than socially kept foals. This suggests that object manipulation and play may function as a substitute for social play for foals reared in isolation from other foals.