Environmental control and potential fate of phytoplankton production were investigated in the Greenland Sea (75 degree N) in June 1989. Phytoplankton biomass, taxonomic composition and production were size fractionated. Total primary production was generally high (up to > 0.9 g C m super(-2) d super(-1)), especially in the Arctic Front. The production per unit biomass P super(B)(z) was a nonlinear function of the vertical distribution of irradiance E(z), especially for the >5 mu m fraction where E(z) accounted for 60 to 97% of the variance of P super(B)(z). Much of the subsurface chlorophyll was probably not photosynthetically active due to limitation by irradiance. There was a marked transition in several variables at the Arctic Front. To the west (Arctic Domain), waters were cooler and slightly less saline than to the east (Atlantic Domain), concentrations of silicate were lower, and total primary production was generally lower. The structure of phytoplankton assemblages (diatoms and dinoflagellates) changed at the front. Results confirmed the previously reported trend of a progressive decrease of phycoerythrin-containing cyanobacteria with increasing latitude. In the Arctic Domain, primary production was generally dominated by cells >5 mu m, but this was not proportionally reflected in the standing stock which was dominated by the <5 mu m fraction.