One standard assumption in the theory of professions involves the notion of a specific occupational group trying to and partly succeeding in controlling the supply of services in a specific segment of society. Each and every profession is then seen as implicitly or explicitly trying to avoid or control the competitive market model. This is the core of the neo-weberian cynical theory of professions, underscoring social closure and monopolies as prime vehicles of professionalization. Another theoretical strand argues the importance of expansion for the entrenchment and success of professions. This paper explores the relation between professional expansion and social closure, focussing on those mechanisms which are concomitant with expansion and arise as a reaction within the jurisdictional fields of rapidly expanding professions.