We report 2 cases of leiomyosarcoma associated hypoglycemia. Case 1 had had a tumor over his left thigh area for 13 years and a few episodes of hypoglycemia occurred when the tumor grew rather large (10 cm x 10 cm x 6 cm). Abdominal sonogram showed metastatic masses in the left lobe of liver. Hypoglycemia syndrome improved after chemotherapy, but relapse was noted later. Another case suffered from progressive abdominal distension for about one year and a huge mass (19 cm x 15 cm x 12 cm) over small intestine was found. Although surgical resection of the tumor and adjuvant chemotherapy was performed, recurrence of the tumor with hypoglycemia was noted. Both of the cases produced hypoglycemia in a fasting state rather than postprandial hypoglycemia. Hypoglycemia associated with non-islet cell tumor is one of the endocrinologic paraneoplastic Syndromes. The most common tumor found in this syndrome is sarcoma and such tumors are usually large when hypoglycemia is noted. Treatment of paraneoplastic hypoglycemia initially requires glucose infusion for acute symptomatic relief, then treatment of the underlying tumor. Reduction of tumor, radiotherapy or chemotherapy can improve the hypoglycemia syndrome, but it readily relapses.