This paper explores the problems of managerial discretion in the non-profit sector, with special consideration to Spanish Work Accident Mutuals (MATEPs). Firstly, from Transaction Costs, Property Rights and Agency perspectives, the economic rationale of mutuals is analyzed, paying particular attention to MATEP’s peculiarities and incentives in terms of competition, regulation and ownership. Subsequently, the effectiveness of governance mechanisms is discussed, showing that the status quo leaves excess power in the hands of the managers of these organizations