A number of health care systems use waiting time as a rationing device for access to inpatient care. However, a considerable amount of research has focussed in particular on the UK's National Health Service and its perceived problem of waiting "lists". In this chapter a theoretical discussion addresses the issue of the optimum wait in the context of Paretian welfare economics. However, reference is also made to public choice analysis and to queuing theory. Empirical literature that explores the various dimensions of waiting costs is reviewed and evaluated. Different methods of estimation are illustrated and these include contingent valuation, implied valuation and econometric modelling. The policy section assesses various "solutions" to the waiting list "problem". Options are classified in terms of their impact on excess demand and the issue of waiting list management is addressed. In the absence of an over-arching welfare analysis both empirical work and policy recommendations are inevitably piece-meal and open to debate. Given the inherent weaknesses of applied welfare economics the challenge is to find a framework which would attract a broader consensus.