Diet and feeding patterns of 10 species of gonostomatid fish in the Rockall Trough and Porcupine Seabight, northeastern Atlantic, were investigated as a part of studies analyzing the meso-and upper bathypelagic micronektonic fish communities in these two areas. Copepods were the major food organisms, composing more than 72% in both areas, and ostracods the second most abundant prey organisms (〉13%). The results of stomach content analyses reveals that most of gonostomatids, including two important species, Cyclothone braueri and C. microdon, feed continuously regardless of light cycle and a little at a time. The gonostomatids appear to be planktivores that consume small-sized prey; relative size of most preys was about one-tenth of fish length. These feeding patterns could be an adaptive characteristic of fish living in great deep water where the food items are scarcely present. In general there are no considerable inter-and intraspecific differences, not to mention regional differences, in the feeding of the gonostomatids at both stations except the large specimen of Gonostoma elongatum fed fish. Thus several coexisting species of the gonostomatid fish utilize the same resources, showing competitive relationships.