The introduction of the horse brought many advantages to medieval English farming, particularly as an improvement to ploughing and hauling. But the replacement of oxen by horses was by means inevitable, as the situation often depended upon a number of factors t immediately obvious to modern eyes. These factors, which included such environmental aspects as soil types and terrain, are evaluated to see how they affected the decision to use horses and oxen. The introduction of the horse is furthermore examined in relation to farm production, the improvement in marketing, and the development of regionalism; and various theories regarding techlogical invation are assessed to see whether this or that invation acted in a predictable way. Most importantly, the study affords a glimpse into the working of the minds of medieval farmers as they approached the problems of livelihood and survival.