In December 1999 the Centers for Disease Control and Prevention's (CDC's) Division of HIV/AIDS Prevention initiated a standardized evaluation system for CDC-funded health department HIV prevention programs. This health department evaluation guidance asks health departments to develop comprehensive evaluation plans and to submit aggregated data on such activities as intervention planning, process monitoring, and outcome evaluation. During the first year of this system, of 65 health departments, 62 submitted evaluation plans, 37 submitted intervention plan data, and 20 submitted process monitoring data. Major issues affecting implementation of a national evaluation system include varying levels of evaluation capacity among health departments, differences between the CDC's taxonomy for national data collection and local definitions, and limitations regarding use of 1st-year data. The CDC has learned that implementation of a standardized evaluation system takes considerable time and that stakeholder involvement and technical assistance and capacity building support are essential.