An IOM workshop on evaluation design drew on recent evaluations of 4 complex initiatives (PEPFAR; the Global Fund to Fight AIDS, TB and Malaria; the President’s Malaria Initiative; and the Affordable Medicines Facility-malaria). Key components for good evaluations: (1) a robust theory of change to understand how and why programs should work; (2) use of multiple analytic methods; and (3) triangulation of evidence to validate and deepen understanding of results as well as synthesis of findings to identify lessons for scale-up or broader application.