The Integrated Air Cancer Project (IACP) is an interdisciplinary research program designed to develop the scientific methods and data sets needed to identify the major carcinogenic chemicals in the atmosphere; to characterize the emission sources and chemical precursors which give rise to the identified chemicals; and to improve the methodology and data available for assessing human exposure and risk due to exposure to airborne carcinogens. The research effort is focused primarily on characterizing the impact of complex mixtures of products of incomplete combustion, including the gaseous, semi-volatile, and particle-bound organic species. The first phase of the project focused on the following: (1) to develop, evaluate, validate, and document the sampling and analysis methods necessary to accomplish the technical research; and (2) to attempt to extend current source apportionment techniques to account for the observed mutagenicity of the collected ambient aerosol samples.