Using Defense Meteorological Satellite Program (DMSP) special sensor microwave imager (SSM/I) sea-ice data and meteorological data, we investigate processes controlling the advance and retreat of sea ice in the Sea of Okhotsk. For this investigation we apply a new algorithm to the SSM/I data, which is capable of calculating ice concentration and distinguishing sea-ice types; this algorithm is confirmed by comparison with National Oceanic and Atmospheric Administration (NOAA) advanced very high resolution radiometer (AVHRR) imagery. Our investigations show that there exists a locality for the areas of new-ice formation, and the ice formation near the ice edge always occurs as a recovery after sea ice has retreated suddenly. We also reveal that the speed of ice-edge advance fairly coincides with that predicted by 2% of the geostrophic wind. Furthermore, there exists a good correspondence between the times when the overall advance and retreat of ice cover begin and the decrease and increase of air temperature begin. We conclude that the advance of the ice cover in the Sea of Okhotsk occurs primarily through ice advection by wind and that the interannual variation in the maximum sea-ice extent can be interpreted by that in wind and air temperature conditions. ¿ 1999 American Geophysical Union