Analysis of feline calicivirus-infected cell extract for large and low molecular weight proteins revealed the presence, in submolar amounts, of a polypeptide of molecular weight 80,000 daltons which had no precursor-product relationship to the capsid proteins (mol. wt 68,000 and 14,000) synthesized in infected cells. Two other highly labelled non-structural polypeptides of molecular weights 80,000 and 40,000 daltons yet to be identified were also described.