Summary1Adolescent, mature and ripe potatoes continue to be distinguished by their respiratory behaviour throughout the period of storage.2When potatoes are placed in storage there is a progressive increase in the concentration of internal carbon dioxide until the termination of the period of dormancy, the percentage of this gas falling rapidly with the commencement of sprouting.3Data concerning the composition of the atmosphere surrounding the tubers show that, in general, there is an accumulation of carbon dioxide in the surrounding air with increasing periods in storage.4There is a negative correlation between R.Q. and the percentage internal carbon dioxide during the stages of dormancy and sprouting.5Records concerning the composition of samples of air withdrawn from top, middle and bottom layers of potatoes show a slightly higher percentage of carbon dioxide in the bottom layer than in the middle and top ones.6Data concerning the permeability of the periderm of the potato to gas during storage indicate that the permeability of the superficial tissues decreases considerably during the dormancy of tubers.