Epidermal growth factor receptor(EGFR)is a transmembrane receptor tyrosine kinase the signaling of which is important for growth and progression of cancer. An exon 19 deletion mutation and an exon 21 L858R point mutation are frequently detected as EGFR mutations in patients with non‒small cell lung cancer. This review summarizes the differences in epidemiological, nonclinical, and clinical characteristics between the exon 19 deletion mutation and the exon 21 L858R point mutation.