Allelic loss on chromosome 13 occurs frequently in esophageal squamous cell carcinomas. To define minimal deletion intervals and find candidate tumor suppressor gene(s), we conducted a study of loss of heterozygosity (LOH) in 59 esophageal squamous cell carcinomas from northern China using a panel of ten microsatellite markers on chromosome 13q. The results showed that 12 of 59 (20%) cases presented allelic loss in three or more consecutive adjacent chosen markers, suggesting loss of larger fragments on chromosome 13q. Two minimal deletion regions of overlap were found: one was located on band 13q12.3 from markers D13S171 to D13S267, and the other on band 13q14.1-q14.3 from markers D13S263 to D13S168. The latter was a new deletion region that was never reported in esophageal squamous cell carcinomas. More frequent LOH was observed in higher pathological grade of esophageal cancer at loci D13S171, D13S263 and in later stage of esophageal cancer at D13S263. The data suggest the possibility that one or more unknown tumor suppressor gene(s) on 13q may play an important role in the development of esophageal squamous cell carcinomas.