The thesis investigates the character and actions of craft guilds in early modern Sicily. Sicilian craft guilds emerged only in few towns and compared to most other European regions were less numerous relative to the total population; they also never had a firm political role in urban administration. The thesis investigates the causes and consequences of this weakness in two directions. First, it examines the operation of the guild system through the actions and interests of individual members, focusing in particular on the craftsmen's incentives to participate in guild activities or alternatively 'free ride'. Second, it analyses the institutional and economic framework within which Sicilian guilds emerged and survived for around four centuries, and discusses the consequences of their weakness. The literature on early modem guilds mostly assumes that they were economically conservative and hindered technological change; the question therefore arises whether technological and manufacturing growth was less constrained in early modern Sicily than elsewhere. The thesis argues that the basic features of the Sicilian guild system were similar to those of craft corporations elsewhere in Europe, and that they were devised primarily to promote skills training through formal apprenticeship rules. It therefore concludes that differences in guild development across societies were largely a function of the institutional context within which guilds were embedded, and in particular of the political support or opposition offered by local and central authorities. In Sicily, the Spanish state was unwilling to support the institutional and legal independence of craft guilds, and local urban elites similarly opposed the rise of strong crafts. Lacking legal backing to enforce membership and apprenticeship rules, Sicilian craft guilds were unable to supply specialised labour in support of a thriving manufacturing base. The lack of a strong craft base was reinforced by Sicily's specialisation in agriculture, and led to the long-term failure of domestic manufactures