Sera from 155 individual Pacific walruses, sampled in the Chukchi Sea during the summer of 1983, were tested for serum-neutralizing (SN) antibodies to 6 marine calicivirus serotypes. Serotypes tested included San Miguel sea lion virus (SMSV) types 1, 5, 8, and 10, isolated previously from northern fur seals in the Bering Sea; walrus calicivirus (WCV), isolated previously from walrus feces collected off sea ice in the Chukchi Sea; and Tillimook calicivirus (TCV), a bovine isolate of suspected marine origin. No antibodies were found to SMSV-1, SMSV-10, or TCV. Antibodies to SMSV-5 were found in 2 animals (titers 1:20 and 1:160); antibodies to SMSV-8 were found in 4 animals (all 1:20); antibodies to WCV were found in 1 animal (titer 1:40). Antibodies to WCV have been reported previously in Pacific walruses; however, this represents the first report of antibodies to any of the SMSV serotypes in this species of marine mammal.