The total multicenter data from trials with inactivated monovalent influenza A/New Jersey/76 virus vaccine in 2,326 normal children were collected and summarized at Vanderbilt University (Nashville, Tenn.). These combined data provided the best measure of the relative antigenicity and reactogenicity of each manufacturer's vaccine. Children younger than 10 years of age were shown to have vaccine-associated reactions to doses of whole-virus vaccine containing as little as 50 chick cell-agglutinating units. Split-virus vaccines were well tolerated in doses eight times as high. No vaccine was satisfactorily antigenic in a single dose. A two-dose regimen of split-virus vaccine was antigenic, and this regimen was not associated with acute reactions.