Among 2000 descendants of an English immigrant to Tasmania, Australia, the diagnosis of multiple endocrine neoplasia type 1 was found to be very highly probable or highly probable in 130 and moderately probable in 22. Another 242 children and siblings were 50% likely to have inherited this dominant gene. In all age groups, especially the elderly, the majority of affected members had symptoms of only one endocrine disorder or were asymptomatic. In teenagers, the most common presentation was pituitary lesions and the second most common presentation was insulinomas. Frequently, pituitary lesions or insulinomas developed before any parathyroid lesions could be detected. Elevation of gastrin levels, usually associated with hypercalcemia, was rarely seen in patients younger than 25 years. The classic presentation with symptoms of multiple endocrinopathy may represent only a small fraction of these patients in the community.