A biochemical and morphofunctional renal study, applying different sessions of rectal ozone before a warm ischemia, was performed. Rats were divided in:!­ control, a medial abdominal incision was performed for the exposure of the kidneys; 2-ischemia, animals with a bilateral renal ischemia (30 min), with subsequent reperfusion (3 h); groups 3, 4 and 5-ozone + ischemia, as group 2, but with previously treatment of 5, I 0 and 15 sessions of rectal ozone, respectively; groups 6, 7 and 8-oxygen + ischemia, as groups 3, 4 and 5, respectively, but using rectal oxygen. A significant decrease of the flow and renal filtration, with high values of fructasamine and phospholipase A, in the ischemia and oxygen groups, with respect to control and ozone groups was obtained. Control and ozone groups, without any statistical difference among them. Morphological alterations were significantly less in the groups pretreated with ozone, with better results for I 0 and 15 sessions.