Gefitinib and erlotinib are commercially available epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) that are widely used for the treatment of non-small-cell lung cancer (NSCLC). Acute severe liver injury, although rare, has been observed in patients receiving these EGFR-TKIs. Some studies have reported that erlotinib treatment does not cause severe liver toxicity in patients with NSCLC who previously presented with severe liver injury during the course of gefitinib treatment. We retrospectively assessed the occurrence of liver toxicity in patients with NSCLC who were receiving erlotinib and had previously presented with severe gefitinib-induced liver injury.Severe liver injury occurred in only 1 of the 8 patients receiving erlotinib treatment. In this case, erlotinib was discontinued because of the onset of grade 3 skin rash and liver injury. After liver function was restored, erlotinib (100 mg) was administered at a lower dose; nonetheless, grade 4 liver injury occurred. Our findings suggest that it is necessary not only to explain the early symptoms of liver toxicity to patients who are receiving erlotinib treatment and have previously experienced gefitinib-induced severe liver injury but also to more closely monitor liver function.