The problems in long-term organ preservation are ischemia and toxicity from metabolic waste. A simple self-perfusing self-cleaning system has been developed that kept the heart, lungs, and kidney functioning for a mean time of 24 hours. Nine adult dogs were anesthetized and artifically ventilated. The heart and lungs were removed en bloc while being perfused by the heart. One kidney was connected to the descending aorta and inferior vena cava. No anticoagulant was used. Another group of six dogs without functioning kidneys was used as the control group. In the experimental group, urine output ranged from 26 to 48 ml/hr, aortic systolic pressures were 80-107 mm Hg, heart rate was 85-100 beats/min, serum potassium content was 3.25-4.40 mmol/l, and serum sodium content was 155-163 mmol/l. In the experimental group, blood creatinine levels decreased from 0.95 to 0.47 mg/dl during preservation; in the control group, blood creatinine levels decreased from 0.96 to 0.79 mg/dl. Lung biopsies in the preparation with the longest survival showed good preservation for as long as 24 hours, and no thrombi were present. This preparation has the advantage of no ischemic time, no foreign material in the circulation, and the ability to automatically maintain acid-base balance and blood electrolytes. The simplicity of this autoperfusion preparation may allow greater transport distance in organ procurement for subsequent transplantation.