Cardiovascular disease outcomes have been associated with exposure to ambient particulate matter (PM) air pollution in many epidemiological studies. Experimental studies have revealed potential mechanisms behind the epidemiological results and many of these studies have revealed changes in the expression of important genes in key biological pathways with exposure to air pollution from fossil fuel combustion. Few epidemiological studies have examined this. We hypothesized that blood cell gene expression levels along biological pathways relevant to cardiovascular outcomes would be associated with traffic-related air pollutant exposures in elderly subjects with coronary artery disease. Available data were collected in a cohort panel study funded by the National Institutes of Health, National Institute of Environmental Health Sciences. Gene expression data were available for 43 subjects with up to 12 weekly repeated measures conducted in three of the four retirement communities in the Los Angeles Air basin where the exposure measurement work took place. Whole blood samples were collected weekly, RNA was isolated and then it was reversed transcribed into complementary DNA for subsequent gene expression analysis using the polymerase chain reaction method. Candidate genes (35) were selected a priori based on biological function and reported pollutant exposure effects. Exposure measurements were conducted in the indoor and outdoor environment of each community and included daily size-fractionated PM mass and PM organic chemical composition, including polycyclic aromatic hydrocarbons (PAH).