Balancing society's multiple and sometimes competing objectives regarding forests calls for information describing the direct and indirect benefits resulting from forest policy and management, whether to address wildfire, loss of open space, unmanaged recreation, ecosystem restoration, or other objectives. The USDA Forest Service recently has proposed the concept of ecosystem services as a framework for (1) describing the many benefits provided by public and private forests, (2), evaluating the effects of policy and management decisions involving public and private forest lands, and (3) advocating the use of economic and market-based incentives to protect private forest lands from development. The concept extends traditional economic theory regarding multiple forest benefits and the use of economic incentives to enhance their provision, by emphasizing ecosystems as an organizing structure for benefits. Although the emphasis on ecosystems is new, challenges in evaluating ecosystem services are similar to those long faced by economists tasked with evaluating forest benefits: (1) defining a typology of ecosystem services, (2) describing and measuring ecosystem services units or outputs, and (3) describing and measuring ecosystem services per unit of values or social weights. This paper is a discussion of why ecosystem services information is needed, why it has not been rapidly forthcoming despite steady advances in benefits estimation methods in recent decades, and what researchers might do to address growing demand for it among policymakers and managers.