Adrenal lesions belong to the spectrum of multiple endocrine neoplasia type 1 (MEN-1) syndrome. However, the prevalence of adrenal involvement, the characteristics, and the clinical management of adrenal lesions have not yet been clearly defined. A total of 66 patients with confirmed MEN1 germline mutations and 1 additional patient with typical manifestations in three organ systems were monitored in a regular screening program that included evaluation of the adrenals (median follow-up 96 months; range 12 to 300 months). Age at the diagnosis of MEN-1 and of adrenal tumors and the clinical characteristics, genotype, treatment, and follow-up of adrenal disease were analyzed. Adrenal lesions were identified in 18 of 67 (26.8%) MEN-1 patients and were diagnosed 5 years later than MEN-1. The median tumor diameter at diagnosis was 3.0 cm (range 1.2-15.0 cm), with most tumors being 3 cm or smaller. Eight patients had bilateral tumors. Ten patients had nonfunctional benign tumors, three had benign adrenal Cushing syndrome, and one patient had a pheochromocytoma. Four patients developed adrenocortical carcinomas (ACCs), three of which were functional. Nine adrenalectomies and one subtotal adrenalectomy were performed in six patients. Three patients with ACC died owing to the tumor. Patients with mutations in exons 2 and 10 developed adrenal tumors significantly more often than patients with other mutations (p <0.01). Adrenal tumors are a common feature of MEN-1 but occur later in the course of the disease. The lesions are often small and nonfunctional and can therefore be managed by close surveillance; others have significant malignant potential and should be considered for surgery when they are 3 cm or larger.