To generate EGFR-TKI-resistant clones from an EGFR-mutant NSCLC cell line, we exposed EGFR-TKI-sensitive HCC4006 cells with EGFR mutation (exon 19; L747-A750del insP) to increasing concentrations of erlotinib (up to 4 μM) for 3 months. The gene discussed is EGFR; the disease is non-small cell lung carcinoma.