We report an unusual case of multiple endocrine neoplasia (MEN-1) presenting with hyperinsulinemia, hypergastrinemia, and hyperparathyroidism. The patient was referred to our. department for further investigation of symptomatic hypoglycemic episodes and repeated nephrolithiasis. Laboratory studies revealed hypoglycemia, hyperinsulinemia, mild hypercalcemia, and hyperparathyroidism. Pituitary magnetic resonance imaging (MRI) and measurements of hypophyseal hormones were in the normal range. Two pancreatic masses, demonstrated on MRI, were removed surgically by means of enucleation and distal pancreatectomy. No hypoglycemic episodes occurred after surgery. After a symptom-free interval of 4 months, the patient had diarrhea and dyspeptic symptoms. Detailed investigation revealed a gastrinoma, which could be detected by octreotide scintigraphy. The gastrinoma was located between the duodenum and pancreatic head as a solitary lesion. Because of the close proximity of the lesion to the remaining pancreatic tissue and the failure of exact localization, we decided against surgery for the gastrinoma. The patient responded well to lansoprazole. The parathyroid glands were removed and half of one gland was implanted into the forearm. The implant functioned property. The patient was discharged under medical treatment.