The miniaturized heart-lung machine consists of commercially available roller pumps, a flexible heat exchanger, a newly devised bubble oxygenator, and polyethylene cannulas and silicone tubes. The minimum and maximal priming volume of the entire system is 4.7 and 16.7 mL, respectively. The efficiency of the system is reflected in an heat transfer coefficient ranging from 0.96 to 0.31 at flow rates between 1 and 20 mL/min, a high value of oxygen uptake in the range of 0.061 mL O2/min mL blood-1, and low blood trauma with plasma hemoglobin concentrations of 47.5 +/- 5.0 mg/dL after 60 min of in vitro perfusion. The system is a simple, reliable, and efficient miniaturized heart-lung machine for use in small animals.