The National Immunization Survey is conducted by the National Center for Immunizations and Respiratory Diseases and the National Center for Health Statistics at the Centers for Disease Control and Prevention. It began in April 1994 in order to collect data on childhood immunization coverage. It uses a list-assisted random-digit-dialing telephone survey methodology of household respondents, and a mailed survey to children’s health care providers. The target population for the survey is children aged 19-35 months at the time of the interview, and the mail-in portion of the survey collects data on all current recommended vaccines and doses. In 1997, the target sample size for each sampling area was 110 children with completed telephone interviews per quarter, and 440 for the year. In total, the survey produced complete interviews for 34,742 children, and adequate provider data for 22,806 of those children.