The multiple disorders endocrine neoplasia syndromes are autosomal inherited disorders characterized by typical associations of tumors of the endocrine glands. Three different syndromes have been recognized, the type 1, the type 2A and the type 2B. The gene of the multiple endocrine neoplasia type 1 has been localized on chromosome 11 region q13, while the MEN 2 gene maps on the pericentromeric region of chromosome 10. The few years since the original mapping of the two disease genes have seen considerable effort by several laboratories to refine the localization of the genes and obtain good flanking markers. This effort has two purposes: 1) better presymptomatic "diagnosis" and genetic counselling based on both very close and flanking markers, and 2) definition of the molecular regions containing the MEN 1 and MEN 2 loci as a necessary first step in positional cloning efforts. In most clinical situations it is possible to identify a haplotype with the mutant allele in the middle. The calculated predictive accuracy of this test is greater than 95% for the two syndromes. Therefore, genetic linkage testing can be used for informed genetic counselling in families affected by multiple endocrine neoplasia type 1 and 2.