The need for assessing noncancer risks for agents to which humans are routinely exposed indoors arises from the large amount of time spent indoors (i.e., employed persons spend about 60% of their time at home indoors, 30% at work indoors, and 5% in transit). Sources ofair poilutants include heating and coolig systems, combustion appliances, personal use products, furnishings, tobacco products, pesticides, biodefluents from humansand animals, and other microbial contamination such as toxins fromn molds. The purpose of this paper is to describe current dose-response a ent mhods appliable to as risk follwing exposure to indoor air uant The role ofstuture-activity riationships in hazard identification is also described.Risk ments from exposure to indoor air pollutants require exposure ssements and dose-response assessments.Dose-response assessment methodologies include the inhalation reference concentration (RfC), structure-activity relationships, dose-rponse models, and the decision analytic approach. The RfC is an estimate (with uncertainty spanning perhaps an order of magnitude) ofa daily exposure to the human population (including sensitve subgroups) that is likely to be without an appreciable risk ofdeleterious effects during a lifetime. The current RfC method provides guidelines for mking the necessary dometric adjustments for gases and aerosols. Human equivalent cocentus for no-observedadverse-effect levels in animals are determined by using mathematical relationships that adjust for regional deposition, solubility, ventilation rate, and blood:air partition coefficients. The RfC methodology exists as an interim methodology.Future scientific advancements are expected to further refine the approach.