A 66-old-male admitted to our hospital was diagnosed multiple myeloma (IgA kappa type, Durie & Salmon stage IIIA) and squamous cell lung cancer (c-T2N0M0 stage I). The function of platelets was within a normal range (11.7 x 10(4)/mm3 and the bleeding time of two minutes), but the function of coagulation was reduced (prothrombin time, 13.1 seconds; activating prothrombin time, 45.1 seconds; and antithrombin III, 65%). The hyperviscosity syndrome was anticipated because of high IgA M protein (6,551 mg/dl). Plasmapheresis with 800 ml of fresh frozen plasma was performed before the left lower pulmonary lobectomy and R1 lymph node dissection. Then the function of coagulation was improved (prothrombin time, 12.6 seconds; activating prothrombin time, 31.3 seconds; and antithrombin III, 75%). IgA M protein was also decreased to 4,696 mg/dl. Postoperative bleeding necessitated a second thoracotomy. The cause of postoperative bleeding was the ablasion of the pleural adhesion due to tuberculous pleuritis as well as bleeding tendency of multiple myeloma. The plasmapheresis performed in this case did not fully improve the bleeding tendency. Cases of cancer complicated with multiple myeloma have been increasing and if an operation is needed, plasmapheresis should be considered. The indication and the extent of hematologic restoration to be achieved should be further investigated.