In the Closed Ecological Life Support System ( CELSS ) concepts which have been proposed up to now, most of the foods to be provided to the crew have been based on plant and vegetable produce. In this paper, a snail breeding module which will serve, as a subsystem of CELSS, to provide the space crew with animal nutrients has been studied. As a source of nutrition for the crew, snails have various advantages over other animal species. Snails can normally be bred in a limited space and they are insensitive to the lack of oxygen and feed. In this breeding module, a species of snail ( Helix pomatia ) will grow, mature, mate and reproduce. In order to minimize the crew's work, automated operations for feeding, cleaning wastes, handling snails and their spawn, as well as for the maintenace of the module, will be applied. A submodule which processes snails for food production is also studied. In addition to automation, other features taken into account are economy from the view point of utilities consumed, and the desirability of a lightweight, compact module. Further, to prevent possible biocontamination, which may originate from lifeforms inside the module, diffusing to pressurized quarters of the space vehicles, a high level of inter-module sealing will be achieved. As a biological study of snails in space, an experiment using snails' spawn in earth orbit is being planned by authors.