The sequential appearance of three polypeptides, molecular weights (MW) 67,000, 70,000, 85,000 in cells infected with canine parvovirus (CPV) was studied by sodium dodecyl sulphate polyacrylamide gel electrophoresis. The viral origin of three polypeptides was confirmed by immunoadsorption using a specific antiserum, and polypeptides of similar MW were also demonstrated in purified CPV virions. A further polypeptide of MW 50,000 was also present in both infected cell extracts and purified virus. However the viral origin for this polypeptide could not be confirmed by immunoadsorption.