Objective: Multiple endocrine neoplasia type 1 (MEN1) is a hereditary disease characterized by a high risk of developing primary hyperparathyroidism, duodenopancreatic neuroendocrine tumors, and pituitary tumors (PITs). It is unclear if having MEN1 leads to psychological distress because of fear of disease occurrence (FDO), thereby potentially affecting quality of life. Design: A cross-sectional study was performed using the Dutch MEN1 cohort. All patients received the Cancer Worry Scale (a score >= 14 reflects high FDO), the Medical Outcomes Study 36-item Short-Form Health Survey (SF-36), and questions on sociodemographic and medical history. Results: A total of 227 of 285 (80%) eligible patients with MEN1 completed the questionnaire. The mean (+/- standard deviation) age was 47 6 15 years. Overall, patients experienced an FDO of 15.1 +/- 4.7, with 58% of patients having a score >= 14. This is higher than reported in previous studies assessing fear of cancer recurrence in different cancer populations (31% to 52%). Adjusted for age and sex, the FDO score was negatively associated with almost all SF-36 subscales. In multivariable analysis, the diagnosis of a PIT, a pancreatic neuroendocrine tumor, and not being employed were associated with FDO (P < 0.05). Patients had higher FDO scores for their family members than for themselves. Conclusion: The majority of patients with MEN1 have FDO for themselves and even more for their relatives. This psychological distress is associated with a lower health-related quality of life. Therefore, in the medical care for MEN1, emphasis should also be placed on FDO and quality of life.