A cDNA coding for a mucin expressed in intestine has recently been cloned (Gum et al. 1989). We describe here the use of this cDNA to map the gene (MUC2) to human chromosome 11 using somatic cell hybrids, and to make the regional localization to 11p15 by in situ hybridization. Analysis of the CEPH (Centre d'Etude du Polymorphisme Humain) families revealed that MUC2 forms part of the tight linkage group on 11p15 which contains HRAS, INS, TH and HBBC.