Diffuse pulmonary ossification (DPO) was a complication of "shock lung" after aortic valve replacement in a 52-year-old man. The relationship of DPO to shock lung is discussed. A possible mechanism for this complication is based on the development of a fibrin-platelet-fibroblastic interaction that may establish an intraalveolar lattice for collagen deposition by the fibroblast. The development of acidosis and mechanical forcer may potentiate fibroblastic transformation into an osteoblast. The mechanical forcer may influence the shape of the bone in the lung.