Multiple endocrine neoplasia (MEN) is a rare autosomal dominant disorder characterised by primary tumours in at least two different endocrine glands. In the early twentieth century, a syndrome that involved the concurrence of tumours of the parathyroid glands, the pancreatic islets and the anterior pituitary gland was described. The gene that codes for menin is located on chromosome 11q12-13 and transcribes an mRNA consisting of 10 exons which encodes the 610 amino acid protein, menin. MEN 2 is a rare disorder with a prevalence of one in 20,000, and like MEN 1, is an dominant syndrome. The RET protooncogene, located on chromosome 10q11.2, transcribes an mRNA consisting of 21 exons. Molecular information has revolutionised the understanding and treatment of MEN 2. The increasing knowledge of the molecular mechanisms of MEN coupled with the clinical outcome and the availability of genetic testing has greatly reduced its morbidity and mortality.