Marine caliciviruses of the genus Vesivirus were first isolated in 1972, and include San Miguel sea lion virus types 1-17 (SMSV1-17), walrus calicivirus (WCV), and cetacean calicivirus (CCV). Vesicular exanthema of swine virus (VESV) has also been shown to be a vesivirus of ocean origin as have a number of other viruses isolated from terrestrial animals; all these viruses belong to a single species, Vesicular exanthema of swine virus. These viruses can induce a wide variety of diseases in pinnipeds including vesicles on the skin and oral mucosa, reproductive failure, abortions, severe diarrhea, myocarditis, and encephalitis; some are also believed to be zoonotic, causing vesicles on the hands and feet of infected humans. Members of the Caliciviridae seem to be in a constant state of evolution prompting the appearance of novel viruses either as a consequence of genomic instability or by the emergence of fitter viruses present within an animal population, due to immunological pressure. We have isolated and sequenced the genomes of two novel genotypes of marine vesiviruses from Steller sea lions (Eumetopias jubatus) from Alaska. While more than 40 different marine calicivirus serotypes have been recognized, the complete genomes for only four viruses are available in the GenBank database. Sequence analysis of the complete genome of these two Steller sea lion caliciviruses and their comparison to available marine vesivirus genomes may provide clues as to the molecular basis for the emergence of new genotypes of marine caliciviruses over time.