An unprecedented revolution has swept over the development scene since the turn of the century: it is market-led and emphasizes the mobilization of private energies, funds and skills. A brand new cast of influential development actors is transforming the state aid monopoly. The development evaluation discipline, shaped by public sector concerns, has not kept pace with this deep-seated transformation. It has failed to deliver adequate and timely evidence about development impact. Nor has it addressed the basic fiduciary concerns associated with private sector funding or tapped the promise of the new information technologies.