Mutations in exons 18-21 of EGFR TK domain were detected in 19 (23%) of the 81 NSCLCs in which there were 12 adenocarcinomas, three bronchioloaveolar carcinomas, two squamous cell carcinomas, one adenosquamous carcinoma, and one other type of NSCLC. The gene discussed is EGFR; the disease is squamous cell carcinoma.