Abstract: A compact system that simulates a pair of human lungs. The lungs can be controlled to breathe spontaneously under a computer program, or the lungs can also be ventilated from a standard mechanical ventilator used in anesthesiology. Lung compliance and resistance can be varied during a simulation exercise to simulate various physiological disease conditions. The unit is compact and will fit into the chest cavity of a mannequin. The device is especially useful for the training of anesthesiologists, especially with respect to ventilating patients.