Radiolaria were sampled from the plankton at 18 stations during two cruises in the Greenland Sea during summer, 1988. A total of 43 species or categories of radiolaria was found, but over 90% of the radiolarian fauna was dominated by adults or juveniles of 4 species: the spumellarian, Actinomma leptodermum and the nassellaria, Amphimelissa setosa, Pseudodictyophimus gracilipes, and Peridium longispinum. The stations sampled ranged from ice-covered areas high in nutrients to open water areas which were depleted in nutrients. These stations encompassed a gradient in the composition of the radiolarian fauna from an assemblage dominated by juveniles and adults of A. setosa and P. gracilipes at the ice edge to one dominated by Actinomma juveniles, A. leptodermum, and P. longispinum in open water. The total abundance of radiolaria correlated with integrated phaeopigment, but not with chlorophyll a. In discriminant function analysis the 'ice edge' radiolarian species listed above correlated well with chlorophyll a and phaeopigments, while the 'open water' species did not. Several water masses occur in the area, which complicates the interpretation considerably, but the data are consistent with the development of a radiolarian population in tempo with, and in all probability linked successionally to the development of the phytoplankton—microplankton bloom.