We tried to study in depth the recovery process in the cortical and the medullary oxygen (O2) consumption of normal and streptozotocin diabetic rat kidneys after ischemia. It was found that the cortical and the medullary O2consumption decreased after ischemia, reaching their lowest levels at 1 day after every ischemic duration in normal and diabetic kidneys. In the period prior to ischemia to I day after ischemia, no significant difference was seen in the decrease in O2consumption between the cortex and the medulla in normal kidney, whereas the medullary O2consumption significantly decreased compared with the cortical O2consumption in diabetic kidney. From 1 day to 4 weeks after ischemia, the increase in the cortical O2consumption was significantly higher than that in the medulla of normal kidney. In contrast, the increase in the medullary O2consumption was significantly higher than that in the cortex of diabetic kidney. Consequently, up to 4 weeks after ischemia, the decrease in the cortical O2consumption was significantly lower than in the medulla of normal kidney, while there was no significant difference regarding the decrease in O2consumption between the cortex and the medulla in diabetic kidney. These results suggest that there is a clear difference in the postischemic recovery process of O2consumption between the cortex and the medulla, and also between normal and diabetic rat kidneys.