Poxvirus has been identified in numerous terrestrial vertebrates as well as in several species of marine mammals, namely seals, sea lions, and dolphins. This is the first reported case of poxvirus infection in the Killer Whale, Orcinus orca. Cutaneous lesions associated with poxvirus infection in the Atlantic Bottlenose Dolphin are commonly called "tattoo" lesions. In this three year old female Killer Whale, the lesions were first noted in March of 1991 and were still present in January, 1992. The gross appearance is similar to that of the dolphin. It begins as a small circular lesion and progressively enlarges. Adjacent lesions may coalesce to form larger areas. The lesions are visible in both pigmented and non-pigmented areas. They are slightly raised on the active borders only, with the exception of a lesion on this animals fluke, which was raised, pigmented and hyperplastic. There have been no behavioral signs of illness in this animal and hematologic and biochemical parameters indicated a mild inflammatory response. There have been no reports of poxvirus isolation from either pinnipeds or cetaceans, and viral culture from this case failed to isolate pox. Diagnosis was based on the histological presence of eosinophilic intracytoplasmic inclusion bodies and by the demonstration of pox virons with electron microscopy. Poxvirus has been seen in both captive and free ranging pinnipeds and cetaceans. It does not appear to be detrimental to cetaceans, and is generally a self limiting disease.