The number and quantities of PAH emitted and accumulated within various environmental media require the development and application of new methods for determining the major routes of exposure to individual and selected compounds. From research that has been conducted on airborne BaP and other selected PAH it appears that they can accumulate indoors as well as outdoors. Smoking seems to be a major contributor for direct and passive inhalation, but the role of cooking and wood burning related to indoor emissions needs to be investigated further. The available data indicate that many PAH will be distributed between both particles and the gas phase. Therefore, new techniques for simultaneously sampling PAH in both phases are required for the indoor environment and personal monitoring studies. These will increase our understanding of the distribution of each component and increase the accuracy of exposure and risk assessments conducted for Total PAH. A strategy (THEES) has been developed for the measurement of BaP exposure from multiple pathways. It should be extended to other PAH, which will assist in quantifying the significance of indoor air related exposures. The inhalation exposures could be derived from indoor combustion sources, penetration of outdoor air indoors, and personal activities, such as cooking and smoking. The reactivity of PAH requires further investigation, since it appears that a number of nitro-PAH will be produced. Some of the resulting compounds will need to be factored into PAH exposure assessments.