During a routine survey of the Pacific oyster Crassostrea gigas in Tongyoung (previously Chungmu) on the southern coast of Korea, basophilic inclusions were observed in the gonadal tissues. They were detected from March to May at a prevalence rate of 3.3 to 7.1%. The inclusion bodies were Feulgen-positive and stained orange-red with phloxine tartrazine. Electron microscopic observation revealed non-enveloped, icosahedral particles 40 to 45 nm in diameter. These morphological characteristics resemble those of papova virus-like inclusions previously described from Pacific and eastern (American) oysters C. virginica in North America. Although many mitochondrial bodies and intact sperm cells were observed around the inclusion body, no host reaction, such as hemocytic infiltration, was detected.