Five new serotypes of calicivirus were isolated from marine mammals. San Miguel sea lion virus (SMSV)-8 and SMSV-10 were recovered from vesicular lesions on the flippers of northern fur seals in the Pribilof Islands of Alaska [USA]. Serotype SMSV-9 was isolated from a sea lion in southern California and SMSV-11 was isolated from 2 northern fur seal pups in southern California. Serotype SMSV-12 was also isolated in southern California from sea lion and fur seal pups.