The HST1 gene has previously been found to be amplified in over 40% of squamous cell carcinomas of the esophagus. We performed Southern blot analyses on squamous cell carcinomas of the lung, nasal cavity, uterine cervix and gallbladder, using HST1, INT2 and five other oncogenes as probes. The HST1 and INT2 genes, both of which were mapped to chromosome 11 at band q13, were coamplified in a squamous cell carcinoma of the gallbladder. The degree of amplification exceeded eight fold.