A majority (85%, 28 out of 33) of non-neoplastic oesophageal epithelium specimens showed negative cytoplasmic and nuclear Id-1 staining, while 36% (29 out of 80) and 29% (23 out of 80) of ESCC specimens showed moderate to strong cytoplasmic Id-1 staining and positive nuclear Id-1 staining, respectively. This evidence concerns the gene ID1 and esophageal squamous cell carcinoma.