Bovine hereditary dilated cardiomyopathy(bcMP) is endemic in Switzerland and hearts from diseased animals display important clinical and biochemical similarities to human DCM. Recent research has identified at least one protein(myoglobin) to be significantly reduced in bovine DCM. Using a proteomic approach, we have separated over 1125 protein species from bovine ventricular tissue. Gel analysis and protein characterisation have identified a number of proteins whose abundance is significantly altered in bovine DCM. Twenty-four proteins are of decreased abundance in diseased tissue, whilst 11 proteins are of increased abundance in the diseased state. A combination of amino acid compositional analysis, peptide mass profiling, N-terminal microsequencing and Multildent(http:/www.expasy chsprotmiltiident.htmD has been employed in order to elucidate the identities of the differentially expressed proteins. Using these techniques we have currently determined the identity of 12 of the 35 altered proteins. We have also detected three proteins that are differentially expressed in genotypically diseased but phenotypically normal animals, identifying a possible mechanism for the onset of the disease. The possibility that inappropriate ubiquination of proteins plays an important role in te disease is discussed. A database of bovine proteins is currently being established. The identity of the proteins affected, together with a comparison of the human and bovine expression pattems, is displayed.