Objective: To calculate the costs of influenza hospitalization at a tertiary care children’s hospital as the basis of a cost-benefit analysis of the new influenza vaccine recommendation for children age 6 to 23 months. Study design: We reviewed the medical records of all patients admitted to Children’s Memorial Hospital (CMH) in 2002 diagnosed with influenza. Total hospital costs were obtained from the Business Development Office. Results: Thirty-five charts were analyzed. Both of the 2 patients requiring mechanical ventilation and 4 of 6 patients admitted to the intensive care unit had high-risk underlying medical conditions. Nine children were age 6 to 23 months; 4 of these 9 had no preexisting medical conditions. Had all 18 high-risk children over age 6 months been protected from influenza, approximately ＄350,000 in hospital charges could have been saved. Conclusions: Preventing the additional 4 hospitalizations in the otherwise low-risk children age 6 to 23 months for whom vaccine is currently recommended would have cost approximately ＄281,000 (＄46child) more than the hospital charges saved. When all children age 6 to 23 months are considered, influenza vaccination is less costly than other prophylactic measures. Addition of indirect costs, deaths, outpatient costs, and the cost of secondary cases would favor the cost:benefit ratio for influenza vaccination of all children age 6 to 23 months. Objective: To calculate the costs of influenza hospitalization at a tertiary care children’s hospital as the basis of a cost-benefit analysis of the new influenza vaccine recommendation for children age 6 to 23 months. Study design: We reviewed the medical records of all patients admitted Total of hospital costs were obtained from the Business Development Office. Results: Thirty-five charts were analyzed. Both of the 2 patients requiring mechanical ventilation and 4 of 6 patients admitted to the intensive care unit had high-risk underlying medical conditions. Nine children were age 6 to 23 months; 4 of these 9 had no preexisting medical conditions. Had all 18 high-risk children over age 6 months been protected from influenza, approximately $ 350,000 in hospital Accepted could have been saved. Conclusions: Preventing the additional 4 hospitalizations in the otherwise low-risk children age 6 to 23 months for whom vaccin When all children age 6 to 23 months are considered, influenza vaccination is less costly than other prophylactic measures. Addition of indirect costs, deaths, outpatient costs, and the cost of secondary cases would favor the cost: benefit ratio for influenza vaccination of all children age 6 to 23 months.