The East Sea or Japan Sea (hereafter, East Sea) is a semi-enclosed marginal sea encompassed by Korea, Japan and Russia (Fig. 1). The East sea has been called “a world ocean in miniature” (Ichiye 1984) because it contains the features and elements of a world ocean, including subtropical and subpolar waters, western boundary currents and their separation. As the open ocean such as the Pacific, the Indian and the Atlantic Ocean has dominant variability from interannual to decadal timescales, not surprisingly, the variability of those timescales in the East Sea has been also reported (Miita and Tawara, 1984, Watanabe et al., 1986, Isoda, 1994, Minobe et al., 2004). Moreover, the East Sea has undergone dramatic changes in recent years (Kim et al., 2001) as the world’s oceans are undergoing secular changes (Levitus et al., 2000). These require more knowledge of the East Sea to better understand detail processes in the World Ocean. So far there are many investigation on the variability of the East Sea in terms of physical, biological and chemical processes (vol 61, Progress in Oceanography). However, the low-frequency variability (i.e., longer than interannual timescales) in the East Sea has not been paid much attention and its nature was not yet fully understood. As one step for this issue this paper addresses characteristics of the low-frequency sea surface temperature (SST) variability of the East Sea using somewhat longer data for the period of 1891-2005.