We identified a primate calicivirus (Pan-1) VPg in Pan-1-infected cells. The Pan-1 VPg was associated with both genomic and subgenomic RNAs. RNase digestion of Pan-1 RNA yielded a residual protein of 16 kDa. The N-terminal sequence of Pan-1 VPg was determined by direct amino acid sequencing and mapped to a region of the genome equivalent to picornavirus VPgs. Alignment of this protein sequence with similar regions of other calicivirus genomes allowed identification of conserved amino acid motifs and potential boundaries of the calicivirus VPg genes. Proteinase K treatment abolished the infectivity of Pan-1 RNA, suggesting that Pan-1 VPg is required for RNA infectivity.