During the winter season of recent years (2001-2004), a new viral infection has become a serious problem of culturing olive flounder, Paralichthys olivaceus in Korea. Clinical signs of diseased fish were dark body coloration, swellen abdomen due to ascites, rectal hernia and congested liver. Based on the morphological and genetic analyses using TEM and RT-PCR, the causative agent was identified as VHSV. Many bullet-shaped virus particles (50-60$ imes$180-200 nm) were observed in heart and kidney of diseased fish by TEM. A representative strain of VHSV, KVHS01-1 showed high pathogenicity against olive flounder (20$pm$3 g) at the temperature lower than 15$^{circ}C$ but not above 18$^circ C$ by artificial infection.