We previously reported definition of a region containing a putative tumor suppressor gene for esophageal squamous cell carcinoma within an approximately 4-cM genomic segment at 9q31-q32. We have investigated this region further using six new microsatellite markers isolated from yeast artificial chromosome clones covering the deleted region and have narrowly defined the commonly deleted region to a segment between two loci, KM9.1 and D9S177. On the basis of the contig map of cosmid and yeast artificial chromosome clones, we estimate the physical size of the region of interest to be about 200 kb. Because the distal 9q region also has been implicated as the site of a tumor suppressor gene(s) related to squamous cell carcinomas of other tissues, our map provides useful information for attempts to identify a common gene for carcinomas of this cell type.