The complex ways in which decentralization is practised in the ®eld of government health services are examined. Organizationally, decentralization means a choice between different types of public institution, which vary in terms of: the areas over which they have jurisdiction, the functions delegated to local institutions; and the way decision-makers are recruited, so producing institutions. There is little agreement about the optimum size of areas, either in terms of population or territory. Areas cannot be delimited without consideration being given to the powers to be exercised at each level. The speci®cation of functions always assumes certain things about who will exercise the delegated powers. The two issues cannot be separated. Five structures of decentralization are distinguished, each of which could in principle be created at regional, district and village/community level: the multi-purpose local authority, the singlepurpose council, the hybrid council, the single purpose executive agency, the management board, ®eld administration, health teams, and interdepartmental committees. Whatever the institutions used for decentralization, the choice of structures and the ensuing process of decision-making will be highly charged politically.