The feline parvovirus subgroup is comprised of viruses isolated from various carnivores, including the dog, cat, mink, raccoon, Arctic fox, and raccoon dog. Those viruses are > 98% identical in their DNA sequences and are very similar antigenically. We have shown that although canine parvovirus (CPV) replicates in numerous feline cell lines in vitro it does not infect cats after parenteral inoculation (U. Truyen and C. R. Parrish, (1992) J. Virol. 66, 5399-5408). Here we use recombination mapping to locate some viral determinants required for feline host range, and show that the ability to replicate in cats was determined by the right-hand 45% of the genome, most likely a function of the capsid protein gene. Efficient replication in the cat appeared to require feline panleukopenia virus sequences from both ends of the VP2 molecule, which contained differences of VP2 amino acid residues 80, 564, and 568. The difference at amino acid 80 was also associated with expression of an FPV-specific antigenic epitope. The differences which affected the feline host range were located in a region of the capsid structure where three VP2 molecules interact, and the mutations gave rise to changes in the conformation of loops of the three adjoining VP2 monomers. The mechanism(s) of the in vivo feline host range restriction were not defined, and we were unable to show in vitro inhibition of virus infectivity by feline serum components or erythrocytes.