The cDNA microarray is an extremely beneficial tool for study of differential gene expression in the cardiovascular system. This technique is used in many different applications including drug discovery, environmental science, and the effects of mechanical forces on vascular cell phenotype. The paper reviews work by others, and describes our study on effects of shear stress on vascular endothelial cells. These microarray studies verified earlier findings using Northern and polymerase chain reaction (PCR) analyses in this area; and also found previously unidentified differentially expressed genes, leading to new hypotheses regarding how cells and tissues respond to biochemical and mechanical stimuli.