David Packard, chairman of the board of trustees of the David and Lucile Packard Foundation and an engineer by training and profession, was personally steeped in scientific method and committed to the belief that public resources should be invested in programs on the basis of evidence. He extended this standard to the foundation's investments and was thus an enthusiastic supporter of the idea of starting a think tank within the foundation that would combine research and grant-making in a multidisciplinary approach to issues affecting children, with the aim of influencing policy and practice. In this article, the author presents a case study of home visitation evaluation at the David and Lucile Packard Foundation, a private foundation which provides grants to home visiting programs for children. The foundation employed an evaluation-focused grant-making strategy over more than a decade in a particular child development service area--the home visitation approach--that illustrates, among other lessons, the management of disappointing evaluation results. (Contains 19 notes.)