Two new virus isolates, one from a California sea lion (Zalophus californianus californianus) and the other from a northern fur seal (Callorhinus ursinus) were partially characterized. Their physicochemical characteristics were similar to those of vesicular exanthema of swine virus (VESV) and San Miguel sea lion virus (SMSV). The virion morphology was in both instances typically calicivirus. On the basis of this and the serum cross-neutralization testing, these isolates were classed as two new types of SMSV and were designated serotypes SMSV-4 and SMSV-5.