A previous study involving widescale genomic profiling in dogs with heart disease has provided a large amount of useful data regarding the pathophysiology and potential etiology of disease. We propose performing oligonucleotide microarray analysis of over 25,000 genes in Great Danes with advanced dilated cardiomyopathy. Microarray studies evaluate of a large proportion of the total canine genome and produce a molecular portrait of the disease process. The proposed study will reveal the transcriptional activity of genes suspected to be involved in the development of DCM, as well as identify new candidate genes that merit further study.