Certain lung diseases, particularly idiopathic pulmonary fibrosis, are associated with altered lung mechanical properties. While adequate techniques exist to measure the lung functions, current methods only provide global measurements of lung stiffness. We have developed a novel surface wave method for noninvasively measuring the viscoelasticity of lungs. In this paper, three types of experiments were carried out on an ex vivo pig lung. The lung was pressurized through a connecting tube to its trachea. The first experiment measured the pressure-volume relation of the lung during the inspiration and expiration. The second experiment measured the surface wave speed of the lung at different pressures. The surface wave was generated by an electromechanical shaker, and the surface wave propagation on the lung surface was measured by a laser vibrometer. The third experiment measured the surface wave speed with an ultrasound linear array transducer.