A 66-year-old man was referred to our hospital with esophageal tumor. He was diagnosed with esophageal small cell carcinoma by endoscopic biopsy. He had a low serum sodium level at admission and was diagnosed syndrome of inappropriate secretion of antidiuretic hormone (SIADH). His CT scan revealed esophageal wall thickness and swelling of thoracic and abdominal lymph nodes. He was classified as Stage IV a (cT3cN4cM0). He received systemic chemotherapy with CDDP and CPT-11. After three courses of chemotherapy, his tumor disappeared on CT scan and endoscopy. He was diagnosed as in complete remission and his SIADH recovered. The patient was then discharged and visited our outpatient clinic. Seven months after diagnosis, a tumor recurrence was indicated by CT scan and endoscopy. He received radiation therapy, and chemotherapy of paclitaxel, followed by CBDCA+VP-16. He is presently alive sixteen months after diagnosis.