Assessment of airborne organic dust in different environments is necessary to better understand the relationship between exposure and disease. Exposure assessment requires a well-defined sampling strategy which addresses the following questions: Where, how long, who, how many, and when? For assessing exposure to organic dust, the question of "what?" must be included because, in most cases, the specific toxins or appropriate surrogates for exposure have not been identified. For most environments with organic dust, these questions have not been adequately addressed. However, a large database exists for cotton dust. Cotton is used as a model of organic dust to illustrate the application of exposure assessment: 1) to develop a dose-response relationship between aerosolized dust and specific health effects; 2) to evaluate the effects of process change on gravimetric dust levels and for compliance with the cotton dust standard; and 3) to identify specific biologically active components in the dust.