Blood is a scarce and costly resource to society.Therefore,it is important to understand the costs associated with blood,blood components,and blood transfusions.Previous studies have attempted to account for the cost of blood but,because of different objectives,perspectives,and methodologies,they may have underestimated the true(direct and indirect)costs associated with transfusions.Recognizing these limitations,a panel of experts in blood banking and transfusion medicine gathered at the Cost of Blood Consensus Conference to identify a set of key elements associated with whole blood collection,transfusion processes,follow-up,and to establish a standard methodology in estimating costs.Activity-based costing(ABC),the proposed allinclusive reference methodology,is expected to produce standard and generalizable estimates of the cost of blood transfusion,and it should prove useful to payers,buyers,and society(all of whom bear the cost of blood).In this article,we argue that the ABC approach should be adopted in future cost-of-transfusion studies.In particular,we address the supply and demand dilemma associated with blood and blood components;evaluate the economic impact of transfusion-related adverse outcomes on overall blood utilization;discuss hemovigilance as it contributes not to the expense,but also the safety of transfusion;review previous cost-oftransfusion studies;and summarize the ABC approach and its utility as a methodology for estimating transfusion costs.