The rate of respiration of red beet slices increased 3- to 4-fold when the slices were aged in a moist atmosphere for 18 to 24 hours. The respiration of fresh slices was severely inhibited by 8 x 10(-5)m HCN but as slices aged the sensitivity of respiration to HCN fell rapidly. The presence of HCN stimulated the respiration of slices after 8 to 12 hours of aging.The relative participation of the pentose phosphate pathway in the glucose catabolism increased very little, if any, during aging of slices prepared from beets in the growing phase although the total metabolic rate seems to be greatly increased. However, data obtained from slices prepared from dormant beets indicated a possible increase in pentose phosphate pathway participation in glucose catabolism upon aging. The activity of 6-phosphogluconate dehydrogenase increased very markedly during aging and a corresponding marked increase in the ability of the tissue to metabolize gluconate was observed. It is concluded that to associate the aging process of storage tissue slices with a specific increase in a particular pathway is not justifiable.