Tumorigenesis in multiple endocrine neoplasia type 1 (MEN 1) involves the unmasking of a recessive mutation at the MEN 1 locus which has been mapped to chromosomal region 11q11-13. By analyzing 58 DNA markers on a panel of radiation-reduced somatic cell hybrids, the region encompassing the MEN 1 gene was divided into nine subregions. Pulsed field gel electrophoresis analysis of markers within subgroups showed that the recombination rate around the MEN 1 locus is high. Combined linkage analysis in MEN 1 families and deletion mapping in MEN 1-related tumors suggest the MEN 1 gene is located centromeric to D11S807 and telomeric to PYGM.