A comparison was made of the activities of several enzymes involved in sugar transformations in potatoes stored both at low temperature and at room temperature. Whole tubers were used, and a technique comparing halves of the same potato was developed. The potato halves and the whole tubers showed similar patterns except the halves went through the pattern more rapidly. The enzymes studied were phosphohexose isomerase, glucose-6-phosphate dehydrogenase, aldolase, and invertase. Within 4 days sucrose accumulated in the potato halves at low temperature followed by increases in reducing sugars. The results could not be explained by a simple lowering of respiration rate at low temperatures. A probable sequence of events appears to be that low temperature induces in the tuber (1) a temporary decrease in aldolase activity, (2) an increase in sucrose, (3) increased invertase activity, (4) accumulation of reducing sugars, followed by (5) a lowering of the activity of phosphohexose isomerase.