These experiments were performed to detect changes in renal function produced by acute infusions of small amounts of ethanol into the isolated kidney of the rat. Ethanol was infused for 10 min beginning at 40 min to reach a final concentration of approximately 80 mg/100 ml in the recirculating perfusate. Control kidneys were perfused for 90 min without the addition of ethanol. Control and ethanol infused kidneys were compared with respect to the following measurements: glomerular filtration rate, urine volume, urine protein concentration, pressure and fractional excretion of sodium, chloride, potassium, calcium and magnesium. Ethanol concentration in the perfusate was measured by gas chromatography. The only parameter affected by these concentrations of ethanol was pressure. During the ten min ethanol infusion, the pressure in the system rose significantly (P less than 0.01) from 110 +/- 0.3 to 120 +/- 2.8 mmHg. After the ethanol infusion, the pressure decreased towards pre-ethanol levels at a faster rate than the decrease in ethanol concentration in the perfusate.