Objective: To describe the annual operational costs of a mature Experience Corps[R] program in elementary schools in the Baltimore City Public School System. Methods: Systematic records of expenditures kept by the community partner, Greater Homewood Community Corporation, to be reported to funders were made available for analysis. Expenditures were aggregated to the level of fiscal year and grouped in categories in consultation with the community partner. Results: Expenditures to provide reimbursement to volunteers and to administer this complex volunteer program in an environment in which the school district needed additional management resources for such a program dominate the total expenditures. In the 2008 fiscal year, the program provided 158,305 hours of older adult volunteer service to public elementary schools in Baltimore City and the cost per volunteer hour was $9.79; in the 2009 fiscal year the program provided 157,238 hours of older adult volunteer service and the cost per volunteer hour was $9.60. This suggests consistency and may also suggest that the program is becoming more efficient over time. Conclusion: The costs presented represent the costs of running a mature program after an initial investment has been made. These costs would need to be compared with the short-term and long-term benefits to the older adult volunteers, the school children, other school personnel, and the schools' and volunteers' communities to perform a comprehensive benefit-cost analysis to inform public policy. (Contains 3 tables.)