The paper discusses the development of guidance for considering cost-effectiveness when selecting and designing indoor air quality (IAQ) control approaches. A program has been initiated to develop technical guidance that will assist the user in selecting and designing the most cost-effective combination of IAQ control options in any specific circumstances. The initial guidance will be general guidance for commercial and institutional buildings, based on a series of case studies. The initial effort has focussed on defining the methodology for developing this guidance. The on-going methodology development efforts described here include definition of: the scenarios for which alternative IAQ control approaches might be considered as competitive options; the methods for calculating cost and effectiveness; and the methods for presenting, in a user-friendly manner, cost-effectiveness as a function of effectiveness in reducing occupant exposure. The case studies that will be conducted, using the methodology, will involve detailed definition of all key building-; heating, ventilation, and air-conditioning-; source; occupancy; and IAQ-related parameters for the given case (e.g., a particular new small office building). A sensitivity analysis will then be conducted.