The high-salinity surface layer of young sea ice was subjected to field and laboratory experiments. Artificial pools, in which young ice was formed, were opened within a fast-ice sheet in the Saroma lagoon, Hokkaido, in February of 1983 and 1984. The salinity of 1 mm thick surface layer of the young ice was observed as high as 42.4‰, which exceeds the seawater salinity of 31‰. The surface salinity increased with rising surface temperature. When a load was placed on the fast ice near the pool, seeped brine of salinity 72.5‰ was observed on the surface of the young ice; and when the load was removed, the brine disappeared. Meanwhile, brine permeabilities, both upward and downward, were measured in the laboratory, Both permeabilities decreased logarithmically with lowering surface temperature. A remarkable anisotropy was observed: the upward permeability was greater than downward, and the ratio of upward to downward premeability increased with lowering surface temperature from 5 at -3 °C to 33 at -5°C. Upward and downward permeabilities in ms-1 were respectively 1x10-4 and 2x10-5 at -3°C, 2x10-5 and 6x10-7 at -5°C, and at -10°C upward permeability was 3x10-7.