In Britain a progressive improvement in the health and parity of potato seed stocks can he traced since the beginning of this century, this improvement being reflected in the steady raising of standards employed in the scheme for the 'Inspection of growing crops of potatoes'. In the present day pattern of potato growing, certified seed potatoes of considerable value are produced annually from Scotland, Ireland and to a lesser extent from high lying areas of England and Wales, and the guarantee of a high degree of freedom from virus diseases, which is embodied in the certification scheme, has no doubt contributed much to the high general level of yield in our commercial varieties. There is, however, still a considerable scope for variation in the value of seed with respect to disease factors and physiological factors as influenced by the conditions of storage. Thus blanking in crops may arise from fungal diseases such as dry rot (Fusarium caeruleum. Lib) and skin spot (Oosnora pustulans. 0 & W) which may develop on the seed tuber during storage and there has been increasing interest in measures to control these diseases. Interest has also grown in the effect of conditions obtaining during the storage phase of the seed tuber on its sprouting behaviour and subsequent plant development. The potato tuber is highly responsive to storage factors and its condition at the time of planting as regards weight 2 losses sustained in storage, food reserves available for further growth and stage of sprout development may vary considerably according to the storage environment. The introduction of storage techniques to give greater control of temperature, recognised as the most important storage factor, developments in sprouting techniques and the use of sprout inhibiting chemicals all afford the opportunity to determine this condition to a much greater extent, but more detailed information is still required on storage factors in their various combinations and in their ultimate effects. To further this end, the present study has been carried out to investigate the effects of variations in storage temperature and the use of sprout inhibiting chemicals, before sprouting at various times or planting direct, on sprouting behaviour and plant development in the field.