Carotid atherosclerosis is a multifactorial pheno-type that is the end product of an array of genetic and environmental causes. Genetic analyses of common carotid artery (CCA) intima media thickness (IMT) and ICA IMT measurements with models incorporating cardiovascular risk factors resulted in significant estimates of heritability for CCA IMT and ICA IMT. The role of MMPs and atherosclerosis are determined on the basis of gene function, rather than gene discovery. Expression of matrix metalloproteinases (MMPs) interstitial collagenase (MMP-1) gelatinases (MMP-2 and MMP-9) and stromelysin (MMP-3) and their endogenous inhibitors (TIMPs 1 and 2) were studied in human atherosclerotic plaques and in uninvolved arterial specimens. There are numerous candidate genes that could feasibly contribute to carotid atherosclerosis. The purpose of the genomewide linkage scan is to conduct a systematic evaluation of the entire human genome using families to examine the similarity of phenotype with sharing of alleles at polymorphic genetic markers.