The authors review empirical studies published between 1990 and 2007 on the topics of public health organization, financing, staffing, and service delivery. A summary is provided of what is currently known about the attributes of public health delivery systems that influence their performance and outcomes. This review also identifies unanswered questions, highlighting areas where new research is needed. Existing studies suggest that economies of scale and scope exist in the delivery of public health services, and that key organizational and governance characteristics of public health agencies may explain differences in service delivery across communities. Financial resources and staffing characteristics vary widely across public health systems and have expected associations with service delivery and outcomes. Numerous gaps and uncertainties are identified regarding the mechanisms through which organizational, financial, and workforce characteristics influence the effectiveness and efficiency of public health service delivery. This review suggests that new research is needed to evaluate the effects of ongoing changes in delivery system structure, financing, and staffing.