An ICES expedition whose core period of observation was between August 15 and September 15 in 1973. The principal objective of this experiment was to describe in detail the kinematic and dynamical processes which lead to the renewal of the sub–Arctic bottom water of the northern North Atlantic across the Iceland–Faeroe Ridge and the Denmark Strait. This experiment, a follow–up to OVERFLOW ’60, consisted of over 1700 hydrographic stations and 52 current meter moorings as well as numerous XBTs, tide measurements and drogue tracking. The chief scientist was J. Meincke of the University of Hamburg.