The spatial pattern of sea surface temperature(SST) fronts and its seasonality are presented for the entire East(Japan) Sea. They are based on semi-monthly sea surface temperature(SST) gradient maps constructed from declouded SST images over the period 1990–1995. Fronts in the East Sea can be assigned to the Subpolar Front (SPF) in its central sea areas and to other fronts along the continental shelves. It is observed for the first time that the SPF, located mostly along about 40°N between 132.3°E and 138°E, bifurcates at both its eastern and western ends. The spatial structure of the SPF shows strong seasonality associated with: temporal variations of a warm eddy off the east coast of Korea; surface cooling due to Siberian cold air south of Vladivostok; and bifurcation of the Tsushima Warm Current west of the Tsugaru Strait. We have also observed an isolated frontal zone trapped by a seamount in the northeastern part of the Japan Basin.