We experienced 2 patients who died early after emergency cardiac operation because of malignant diseases. In one case, we operated on a 67-year-old woman for infective endocarditis and performed aortic valve replacement, but she died of terminal pancreatic cancer on the 26 postoperative day. In the other case, a 53-year-old woman underwent emergency operation for cardiac tumor of the left atrium. However, the tumor was diagnosed as cardiac sarcoma during the operation, and it could not be completely resected. The sarcoma recurred after 2 months and she passed away. An emergency cardiac operation without enough preoperative examinations sometimes causes a poor prognosis.