Fission-product nuclides 134Cs, 137Cs and 103Ru originated from the Chernobyl accident have been detected in sediment traps deployed at mid-water depths ranging from 110 to 780 m in the N. Pacific and the Bering Sea. The detected radioactivities, originally associated with fine airborne particles, have apparently been incorporated into much larger aggregates of predominantly biogenic material formed in the surface ocean, and transferred downward through the water column with velocities of the order of 100 m/day. ¿ American Geophysical Union 1988