This qualitative study examines the experiences of four nonprofit human service organizations engaging in performance measurement processes to satisfy accountability requirements and increase organizational and program effectiveness. Nonprofits are increasingly required to respond to performance measurement mandates issuing from multiple sources. However, many of the recommended strategies have been developed in the for-profit and public sectors, and are less appropriate or feasible for nonprofit organizations. Three central findings emerged from interviews, focus groups, and review of archival data. First, the complexity of human change processes and the variation among individual clients complicate efforts to define client outcomes. Second, staff skills play a critical role in effective utilization of data systems. Third, organizational strategies to support performance measurement include incorporating user perspectives into system design and providing adequate staff access to data.