We studied the immunogenicity of the 1992-1993 trivalent split-virus influenza vaccine in pediatric solid organ transplant recipients (PSOTRs) and their healthy siblings. One month after immunization, 41 (82%) of 50 subjects achieved protective titers of antibodies to influenza A, and 30 (60%) to influenza B, rates similar to those in healthy siblings. Achievement and persistence of protective titers occurred significantly more often in children with preexisting antibody. We recommend annual immunization of PSOTRs, their household contacts, and health care workers; immunologically naive PSOTRs may benefit from immunization before transplantation. (J PEDIATR 1995;127:957-60).