A study to determine the prevalence of fish disease in the Bering Sea revealed lymphocystis disease in yellowfin sole (Limanda aspera). The gross pathology and histopathology of typical nodules are described. Electron microscopic studies revealed characteristic icosahedral lymphocystis virus particles, as well as clusters of intracellular structures of uncertain origin. This study begins a larger effort to understand the effects of an altered marine environment upon the biology of lymphocystis virus infection in the Bering Sea. Key words: lymphocystis, pleuronectids, yellowfin sole, Bering Sea, flatfish.