Mounting evidence exists that the activation of proto-oncogene by somatic mutation plays an important roles in the development of human cancers. Recent reports revealed that the kinase domain of ERBB2 gene, a proto-oncogene, is somatically mutated in the lung adenocarcinomas, suggesting the mutated ERBB2 gene may act as an oncogene in human cancers. The purpose of this was to see whether the ERBB2 kinase domain is mutated in other lung cancer types besides the adenocarcinoma. Here, we performed mutational analysis of the ERBB2 kinase domain by polymerase chain reaction-single strand conformation polymorphism assay in 114 non-adenocarcinoma type non-small cell lung cancers (NSCLCs) tissue samples, including 100 squamous cell carcinomas, three adenosquamous carcinomas and 11 large cell carcinomas. We detected the ERBB2 kinase domain mutation in one squamous cell carcinoma (1.0%). The detected ERBB2 mutation showed G to C transversion at bp 2305 (2305G>C), which would result in the substitution of Asp to His at codon 769 (D769H). The amino acid D769 is located in the alpha-helix within the kinase domain, which is important in the binding of ATP with ERBB2. We simultaneously analyzed the somatic mutations of EGFR, K-RAS, PIK3CA and BRAF genes in the squamous cell carcinoma with the ERBB2 mutation, and found that the tumor did not harbor any EGFR or ERBB2 or K-RAS or PIK3CA or BRAF gene mutation, either. This study demonstrated that in addition to lung adenocarcinoma ERBB2 kinase domain mutation could occur in lung squamous cell carcinomas, and suggested that alterations of ERBB2-mediated signaling pathway by ERBB2 mutations may occasionally contribute to the development of lung squamous cell carcinomas.