The postanaerobic behavior of sweet potato roots from a flood-tolerant cultivar, 'Centennial,' and a flood-susceptible cultivar, 'Caromex,' was studied. High concentrations of CO2 and low concentrations of O2 were present in the internal atmosphere of 'Caromex' roots even after the anaerobically pretreated roots were restored to air for a few days, whereas in 'Centennial,' the internal gas atmosphere was less affected by anoxia. Ethanol accumulation in 'Caromex' was consistently higher than in 'Centennial,' and the postanaerobic changes were different between cultivars. An inducation of electrolyte leakage was observed from both cultivars immediately after roots were exposed to a CO2-enriched environment for 48 h. The leakage became greater in 'Caromex' after a 3-day aerobic exposure. In 'Centennial,' leakage of electrolytes due to CO2 treatment diminished at the end of 3 days. Application of ethanol to the discs had no immediate effect on electrolyte leakage in either cultivar under a N2 environment. However, anaerobiosis alone resulted in higher electrolyte leakage. It remains to be determined that the postanaerobic patterns of 'Caromex' and 'Centennial' are characteristic of flood-susceptible and flood-tolerant sweet potato cultivars in general.