This paper describes the design, operation and working characteristics of a multi-purpose sampler which has been developed at the Lowestoft Laboratory and used extensively during the last four years. It was designed in the first instance for quantitative research into the biology of the North Sea plaice, the requirement being for a device that would sample simultaneously and in the same way the abundance not only of plaice eggs and larvae, but also that of their planktonic competitors and predators and, in particular, their food organisms. The sampler is 2·44 m in length and 76 cm in diameter. It is fitted with interchangeable conical nylon nets which vary in mesh size from 0·560–0·270 mm. The filtration efficiency of the sampler ranges from 80·2% to 95·1%, depending on the nose-cone aperture and the net used. The sampler is normally operated at a speed of 5 knots, but it has been towed over the speed range 2·5 to 8 knots and remained stable.