A family of multiple endocrine neoplasia type I with five confirmed cases in three generations is described. All of them have primary hyperparathyroidism in common. The propositus is 51 year-old male. After a year of symptoms of gastroduodenal ulcer, he was found to have elevated levels of serum gastrin and PTH. The serial imaging studies revealed a tumor in pancreatic head, and Zollinger-Ellison syndrome was diagnosed. The gastrin level was reduced into normal range after extirpation of the tumor, but post surgical elevation of Calcium put the patient under parathyroidectomy, which normalized serum PTH and Calcium levels. His two sisters (I and II), the mother of them, and the daughter of sister I, had neither signs nor symptoms until family study showed hypercalcemia in all. Sister I is a 54 year-old female with enlarged parathyroid. The hyperparathyroidism is of chemical type, but no other endocrinological abnormality is found. The Calcium level decreased after parathyroidectomy. Sister II is a 56 year-old female. The only sign was galactorrhea. Serum PTH and Calcium decreased after parathyroidectomy. The prolactinoma was diagnosed by the increased prolactin levels and enhanced mass lesion in sella turcica. Her serum prolactin levels is now within normal range since she is on bromocryptine. The mother of the above three siblings and the daughter of the sister I are now under further study.