Аннотация:Theory-based evaluations have helped open the ‘black box’ of programmes. An account is offered of the evolution of this persuasion, through the works of Chen and Rossi, Weiss, and Pawson and Tilley. In the same way as the ‘theory of change’ approach to evaluation has tackled the complexity of integrated and comprehensive programmes at the community level, it is suggested that a theory-oriented approach based on the practice of realistic cumulation be developed for dealing with the vertical complexity ofmulti-level governance.