A 60-year-old man referred on September 1, 2002, for a 1-month history of nonresponsive dyspnea had undergone radiotherapy for laryngeal cancer at age 44 and surgery for esophageal cancer followed by chemotherapy with cisplatin 100 mg+5-fluorouracil 5000 mg+leucovarin 150 mg at age 56. Blood examination showed a white blood cell count of 2100/μl, red blood cell count of 1650, 000/μl, hemoglobin of 5.8 g/dl, and platelet count of 46, 000/μl, indicating pancytopenia. Recurrence of esophageal cancer with disseminated intravascular coagulation syndrome was initially suspected and imaging conducted, but no findings of recurrence were found. Bone marrow puncture showed significant morphological abnormality of blood cells and complicated chromosomal aberration. Secondary myelodysplastic syndrome was considered. We diagnosed a secondary tumor with poor prognosis appearing 6-8 years after chemotherapy and radiotherapy. Successfully differentiating this case from recurrent esophageal cancer, however, led to good quality of life for the patient.