A computer model, called RISK, for calculating individual exposure to indoor air pollutants from sources is presented. The model is designed to calculate exposure due to individual, as opposed to population, activity patterns and exposure use. RISK is the third in a series of indoor air quality (IAQ) models developed by the Indoor Environment Management Branch of U. S. EPA's National Risk Management Research Laboratory. The model uses source emission and sink models developed as part of EPA's indoor source characterization research program. The source emissions models provided by the model include empirical first and second order decay models and mass-transfer models. The model allows for consideration of the effects of room-to-room airflows, air exchange with the outdoors, and air cleaners on the concentration-time history of pollutants. Comparisons of model predictions with data from experiments conducted in EPA's IAQ test house are discussed. The model predictions are generally in good agreement with the test house measurements.