As public health struggles to define its role within health care reform, the need to examine carefully the component organizations providing and/or supporting health care for the public appears critical. This article identifies the nature and extent of involvement by agencies other than the official local public health department in performing public health practices and functions within 63 local public health jurisdictions. Adequacy of overall public health performance is significantly related to the extent of participation of outside agencies. Outside agencies contribute over 26 percent to the total public health performance for the jurisdictions surveyed. Other agencies of government, both at the state and local level, are the predominant outside contributors to public health practice. Private and voluntary agencies are perceived as minor contributors. Little variation exists among communities in which outside agencies tend to perform particular public health activities. Findings suggest that local public health departments can maximize their impact by understanding better the nature of working relationships within multi-institutional arrangements, encouraging greater levels of collaboration and integration and acting as catalysts for increased support of public health activities.