In this study, profiles of epidermal growth factor receptor (EGFR) and Kirsten ras sarcoma (KRAS) mutations and response to erlotinib therapy have been investigated in patients with non-small cell lung cancer (NSCLC). DNA from 300 patients with NSCLC was extracted from paraf-fin-embedded tissues. After the extracted DNA was sequenced by pyrosequencing method, a total of 97 (32.0%) patients out of 300 were detected to carry an EGFR mutation and 75 (25.0%) patients out of 300 carried a KRAS mutation; 20 (6.6%) patients were detected to carry both of EGFR and KRAS mutations. The EGFR mutations were found to be statistically significant in female patients (48.0 women