Of the four modes of treating human allergic disease, avoidance or separation of the allergic patient from the allergen source is most effective and least expensive. The clinical immunology laboratory has established efficient and inexpensive "reservoir" dust sampling and processing procedures to obtain a surface dust specimen that reflects the allergen burden of the environment. Following extraction, allergens are quantified by reproducible, validated immunoenzymetric assays for the quantification of "indicator" aeroallergen levels in home, school, and work environments. In this paper, the strategies and methods for collecting and processing dust samples are discussed, and assays are reviewed for quantifying indoor aeroallergen exposure from dust mites (Der p I and 2, Der f I and 2), animals (cat: Fel d I; dog: Can f 1; mouse: Mus m 1; rat: Rat n 1), and insects (cockroach: Bla g I and 2). Accurate quantification of the levels of allergen in indoor environments facilitates avoidance therapy by identifying environmental risk factors for asthma and allergy exacerbation and allowing the allergic patient to monitor the effectiveness of environmental remediation actions.