Summary: Pursuant to a congressional request, GAO provided information on the U.S. Customs Service's costs to provide inspection services, focusing on: (1) the user fees implemented at selected federal agencies; (2) the feasibility of developing a model for evaluating the costs of alternative staffing approaches; and (3) whether Customs has developed cost estimates for those services for which it charges user fees. GAO noted that: (1) the two types of user fees that Customs assesses for inspectional services are those established by the Consolidated Omnibus Budget Reconciliation Act and the commerce-related merchandise processing fee, while other federal agencies assess their own user fees; (2) although it would be feasible for Customs to develop a model for evaluating the costs of alternative staffing approaches, it would be difficult for Customs to implement the model, since applicable data is not readily available; and (3) although Customs has developed a model to determine the costs for inspection services for which it charges user fees, the cost data is unreliable.