Immunization registries are confidential, population-based, computerized information systems that collect vaccination data about all children within a geographic area. Registries are key tools used to increase and sustain high vaccination coverage by providing complete and accurate information on which to base vaccination decisions. Registries consolidate vaccination records of children from multiple healthcare providers, identify children who are due or late for vaccinations, generate reminder and recall notices to ensure that children are appropriately vaccinated, and identify provider sites and geographic areas with low vaccination coverage. One of the national health objectives for 2010 is to increase to 95% the proportion of children aged <6 years who participate in fully operational population-based immunization registries (objective 14-26). CDC analyzed data from 50 states and the District of Columbia (DC) from the calendar year 2000 Immunization Registry Annual Report (CY 2000 IRAR) to assess current registry activity. This report summarizes the results of those analyses, which indicate that 32 (63%) of the 51 grantees are operating population-based immunization registries (Figure 1). These 32 projects represent 49% of the U.S. population aged <6 years.