AbstractThe sampling unit described consists of a plexiglass tube which cuts out an area of 3 cm² from the sea-floor. The sample, which may be several em long, is prevented from dropping out of the tube by a small rubber ball being pulled against the tube end by a perlon fishing line which runs up through the core and the tube.A special triangular frame which will hold three sampling units is also described. Although originally designed for sampling benthic diatoms the sampler has also proved to be very suitable for quantitative sampling of other unicellular organisms such as foraminifera as well as for certain groups of the meiobenthos which occur in large numbers, as for example nematodes and harpacticoids.