Multiple endocrine neoplasia type 1 (MEN 1) is characterized by the combined occurrence, to variable degree, of hyperparathyroidism (HPT) (85.7% of cases according to the French Registry of GENEM 1), tumors of the endocrine pancreas (49.6%), pituitary adenomas (38.4%) and, less frequently, adrenal tumors (9.6%) and neuroendocrine tumors (5.8%). Currently, diagnosis of MEN 1 is done in the fourth decade of life, but familial screening (using genetic tools whose diagnostic accuracy approaches 100%) has lowered the age of diagnosis. Screening for MEN 1 in a patient harboring an apparently sporadic tumor will depend on the endocrine gland involved. Extensive screening for MEN 1 in the presence of HPT will be conducted only when the familial history is suggestive, when parathyroid glands are hyperplastic or when multiple parathyroid adenomas have been found at surgery. All patients with an endocrine pancreas tumor need to be investigated for the presence of other endocrine lesions of MEN 1. Extensive screening for MEN 1 is only recommended when a patient with a pituitary tumor or an adrenal tumor has a familial history suggestive of MEN 1. Otherwise regular measurement of blood calcium and PTH levels seem sufficient. Extensive screening for endocrine lesions when MEN 1 is suspected involves hormone measurements and imaging procedures. For the diagnosis of HPT, calcemia and PTH 1-84 must be measured. In the absence of clinical symptoms, basal measurement of serum gastrin, glucose, insulin, glucagon, VIP, somatostatin and pancreatic polypeptide levels are combined with abdominal ultrasonography. When symptoms suggest the Zollinger-Ellison syndrome, the secretin stimulation test is recommended. The diagnosis of a pituitary tumor is made by pituitary imaging and selected hormone assays (mainly PRL). To detect an adrenal tumor, CT scan is recommended, combined with serum potassium, urinary free cortisol and androgen measurement. When the diagnosis of MEN 1 is made, clinical and hormonal follow-up (once a year) and imaging surveillance (every 3-5 years) may be sufficient to detect new other endocrinopathies (unless suggestive clinical symptoms arise). Surgical management of each endocrine lesion must be done by skilled surgeons according to therapeutic protocols which have been discussed in detail. Genetic screening is an integral part of familial screening which may be conducted in collateral and in the offspring of MEN 1 patients. Obviously ethical principles (informed consent, etc.) must be respected. As it is now possible to detect presymptomatic gene carriers with a high degree of accuracy, follow-up is needed to make appropriate management decisions. The marked anxiety provoked by screening in an overtly asymptomatic healthy subject must not be underestimated. Conversely, a negative genetic diagnosis helps to reassure the subject and avoid repetitive and costly follow-up.