Permanent buildings of a variety of designs have been in widespread use for many years as potato stores on the Continent of Europe and in the United States of America. (For a summary of recent literature, with references, see Rose & Cook, 1949.) There are examples of buildings being used as potato stores in this country (e.g. Keith, 1941), but the bulk of the crop is stored in clamps. Because the climates of the U.S.A. and the Continent of Europe differ markedly from that of Great Britain, it is not possible to use the types of store developed in those regions as models for British stores. Over much North America and the Continent of Europe the stores are designed to withstand severe winter frosts, and the main problem is to keep the temperature of the tubers high enough to prevent freezing, the metabolic heat being readily removed if necessary by a small amount of controlled ventilation. Under British conditions the mean daily temperature for most of the storage season, above the optimum for potato storage (40·42° F.), and therefore the main problem is that of keeping the tubers cool. This could, of course, be achieved by using a cold store, but cold storage is considered too expensive. To design a store, information is required about the temperatures attained by stacks of potatoes at different times of the year, the effectiveness ventilation in controlling the temperature, the relation of temperature in different parts of the stack to dimensions of the stack, and to the insulation both of the bin and of the building. To obtain this data a programme of work was initiated, and the results of the first year's work in a building of very low insulating capacity are described in this paper. The climatic conditions during this year, i.e. 1946–7, were very abnormal, a very cold winter followed by a hot spell in the spring which provided an abnormally severe test of an uninsulated store. Later papers will consider storage in an insulated building with adequate ventilation.