Ex post Impact assessments (epIAs) have long been produced by research centres of the Consultative Group oil International Agricultural Research (CGIAR Fund) with a principal stated goal of informing the funding decisions of donor agencies, but there has been little formal analysis of the extent to which epIAs actually do so. To address this Issue, the present analysis investigates how epIA results contribute to donor decisions via three techniques: comparison of epIA results with Subsequent fundi patterns: an email Survey of CGIAR Fund donors; and interviews of donor representatives. Comparison of aggregate estimates from large economic epIAs with funding patterns revealed little correlation between assessed impact and subsequent relative funding levels. Email Survey responses indicate high demand for metrics directly related to poverty and which are 'far down the impact pathway'. EpIAs arc also reported as important in allocation decisions. Interviews of donor officials revealed that factors Such as political priorities., perceived scientific quality and desires for continuity often Influence funding decisions more than consideration of past impacts. In this context, the influence of epIAs is often indirect and "Conceptual'.