Combined clinical and laboratory investigations of MEN-1 have resulted in an increased understanding of this disorder, which may be inherited as an autosomal dominant condition. Defining the features of each disease manifestation in MEN-1 has improved patient management and treatment and has facilitated a screening protocol. Application of the techniques of molecular biology has enabled the identification of the gene causing MEN-1 and the detection of mutations in patients. The protein encoded by the MEN1 gene has been shown to be involved in the regulation of JunD-mediated transcription, but much still remains to be elucidated. Recent advances permit the identification of mutant MEN1 gene carriers who are at a high risk for this disorder and who require regular and biochemical screening to detect the development of endocrine tumors.