The review focuses on strategies for assessing the toxicology of indoor air pollutant mixtures. These strategies are illustrated by reviewing the current problems and approaches to the toxicology of indoor air pollutants from three indoor source categories which make a major contribution to human exposure: environmental tobacco smoke, combustion emissions, and volatile organic compound (VOC) mixtures from materials and products. The strategies include assessment of: exposure and dosimetry, toxic effects of mixtures, causative agents in mixtures, and the predictability of toxicology from one mixture to another. Case studies from indoor air pollution are used to illustrate these strategies. Environmental tobacco smoke research on exposure and dosimetry illustrates new methods using biological markers. Unvented combustion sources such as kerosene heaters emit genotoxic incomplete combustion products and recent research is focused on identifying the genotoxic (causative) agents in these mixtures.