To determine if specific levels of vaccine cost and effectiveness exist that would support eventual respiratory syncytial virus (RSV) vaccine use in the elderly, a cost-effectiveness study was conducted comparing yearly administration of a hypothetical RSV vaccine among the 65-year-old US cohort to medical management of disease. Using base case assumptions - including a vaccine effectiveness against RSV-related hospitalization and death of 80% and a vaccine cost of US$33 - vaccine would result in 0.7 additional days of healthy life at a cost of US$9.82 per person. The cost per quality-adjusted life-year gained equaled US$5342 and remained reasonable over a wide range of vaccine cost and effectiveness. RSV vaccine would be cost-effective for the elderly population, with cost-effectiveness ratios similar to those for influenza vaccine.