Immunization registries are confidential, computerized information systems that contain information about immunizations and children. Registries remind parents when their child is due or overdue for a vaccination, assist providers in identifying their patients who require an immunization, and forecasting which immunization(s) a child may require. Registries also help assess immunization coverage and identify pockets of need. One of the greatest challenges in developing an immunization registry is balancing the need to gather and share information to protect the health of the public and provide clinical benefit to children, with the necessity of protecting the privacy of patients, providers, and other system users. Registry participants must feel confident that their health care information is protected from unauthorized access and disclosure, and that information will be used for the purposes for which it was disclosed. Legislation and technical security measures are not sufficient for protecting privacy. Written confidentiality policies protect the privacy of registry participants and the confidentiality of information contained in the registry.