Compares the sea surface temperatures (SSTs) derived from NOAA/AVHRR data through the multi-channel sea surface temperature (MCSST) algorithm with the in situ SSTs reported from ships and buoys during November 1988-May 1991. The satellite-derived SSTs are lower than the in situ SSTs by more than 0.5°C on the average in the Yellow Sea, the north of the Japan Sea and around the Kuril Islands. On the other hand, the satellite SSTs are higher than the in situ ones by more than 0.5°C in the regions of the Tsushima and Tsugaru warm currents. Furthermore, the most dominant variation of the differences is an annual cycle in the regions north of 40° latitudinal line. The systematic biases may be related to vertical temperature structures in the ocean surface layer, formed by the strong monsoon.