Field studies to determine the effects of a large dose of water miscible vitamin A on selected parameters of children's immunological function were completed in rural Bangladesh. There was no difference between vitamin A treated or control groups in tetanus antitoxin responses after tetanus toxoid immunization or in skin test reactivity to common antigens. Subsequent studies with mice demonstrated vitamin A dose-related antitoxin responses, but the animals required amounts of vitamin that would be likely cause undesirable side effects if administered in similar doses to children.