This article develops a measure of user capacity called Public Service Efficacy (PSE), which is applied to four sectors: hospitals, elementary schools, day care, and higher education. Tests of validity and reliability indicate good properties and consistent patterns across three of four sectors. The measure differentiates between users of the same services, and it increases with level of education. This indicates that PSE can enable us to identify individual users with low capacity and sectors with low average user capacity and thus improve our ability to address equity concerns and harvest potential benefits from user involvement in public service provision. © 2012 Copyright Taylor & Francis Group, LLC.