Renal hemodynamics and function were assessed in 10 anesthetized newborn rabbits undergoing acute hyperoxemia for 1 h. The hyperoxemic period either followed (group 1: n = 5) or preceded (group 2: n = 5) a normoxemic control period. Renal blood flow (RBF) and glomerular filtration rate (GFR) were assessed by the clearance of p-aminohippuric acid and inulin, respectively. Urine flow rate, GFR, RBF, renal vascular resistance, filtration fraction and sodium fractional excretion remained unchanged throughout the study whatever the order of the normoxemic and hyperoxemic periods. It is concluded that hyperoxemia up to PaO2 of 170 mm Hg does not alter renal function.