To understand epidermal growth factor receptor (EGFR) and KRAS alterations among tissues of lung cancer patients in Taiwan, and to further understand how they are related, we used tumor tissues from the non-small cell lung cancer patients and performed a complete analysis. In the experimental results, coexisting EGFR and KRAS mutations were found in 1% (2/180) of the samples. This shows that these mutations tend not to coexist. Furthermore, nearly no coexistence was found between KRAS mutations and EGFR overexpression. These outcomes greatly assist the efficacy prediction of current anti-EGFR drugs for cancer patients.