This study reviews the experience of decentralization in four developing countries: Ghana, Uganda, Zambia and the Philippines. It uses two analytical frameworks to describe and compare the types and degrees of decentralization in each country. The first framework specifies three types of decentralization: deconcentration, delegation and devolution. The second framework uses a principal agent approach and innovative maps of 'decision space' to define the range of choice for different functions that is transferred from the centre to the periphery of the system. The analysis finds a variety of different types and degrees of decentralization, with the Philippines demonstrating the widest range of choice over many functions that were devolved to local government units. The least choice was transferred through delegation to an autonomous health service in Ghana. Uganda and Zambia display variations between these extremes. There was insufficient evidence of the impact of decentralization to assess how these differences in 'decision space' influenced the performance of each health system. The authors suggest that this is a major area for future research.