This paper examines the relationship between human resource practices, operational outcomes, and economic performance in call centers. The study draws on a sample of 64 call centers serving the mass market in a large telecommunications services company. Surveys of 1,243 employees in the 64 centers were aggregated to the call center level and matched to archival data on service process quality, as measured by customer surveys; call handling time, revenues per call, and net revenues per call. Our path analysis shows that human resource practices emphasizing employee training, discretion, and rewards lead to higher service quality, higher revenues per call, and higher net revenues per call. In addition, service quality mediates the relationship between human resource practices and these economic outcomes. There is no significant relationship between HR practices and labor efficiency, as measured by call handling time; and labor efficiency is inversely related to revenue generation.