This paper is an overview of sheep transhumance in southern Italy from the Aragonese reform of the 1440s to the eve of a second wave of reforms in the 1540s and 1550s. The analysis focuses on the concept of mobility, which proves to be a significant indicator of increasing interdependence between the factors involved in this complex economic activity (agriculturists, pastoralists, the state, the merchants, the market and local communities), leading to change in settlement patters, production arrangements, merchant networks, social identities, economic and political thought. The role of the state institution of the sheep custom house in coordinating the seasonal movement of sheep, graziers, officials and merchants, and in negotiating the multiple, overlapping claims of landlords, towns, the state itself and pastoralists on the same lands was pivotal in the long-term survival of this economic sector.