Considerable theoretical and empirical progress has advanced our understanding of the role and value of the volunteer, resulting in improved estimates of volunteer labor valuation. Yet this task still involves conceptual and methodological challenges. Conceptually, costs and benefits accrue to the organization, the volunteer, and to society. Depending on one’s purpose, the focus may be on one or more of these concepts. To date, researchers have pursued three approaches: opportunity cost, replacement cost, and organizational value. Methodological challenges result from a lack of consensus on how to define volunteerism. There is still no comprehensive assessment of methodological differences for counting volunteer hours and researchers have not clearly documented which approaches yield the most accurate estimates. More generally, on-going analysis of volunteer hours in national datasets is largely missing and research that directly measures either the replacement value or the organizational value of volunteers is in its infancy.