Previous studies have demonstrated that both gefitinib and erlotinib are markedly effective for the treatment of non-small-cell lung cancer (NSCLC) with somatic activating mutations of the epidermal growth factor receptor gene (EGFR-mt). These agents are considered to act on EGFR through the same mechanism. However, the efficacy of these agents against EGFR wild-type (-wt) NSCLC remains unclear, and the frequency of adverse events (AEs) appears to differ between them at each approved dose. Here, we conducted a retrospective analysis of AEs and drug efficacy in patients with NSCLC whose EGFR mutation status had been confirmed and who all received 250 mg gefitinib or 150 mg erlotinib once daily. The erlotinib group (n = 35) had more AEs, including rash, fatigue, stomatitis, anorexia and constipation. On the other hand, liver dysfunction and nail change were more frequent in the gefitinib group (n = 107). AEs of ≥grade 2, including rash, fatigue and nausea, were more frequent in the erlotinib group. The erlotinib group also showed more of a tendency to require dose reduction due to AEs. With regard to treatment efficacy for patients with EGFR-wt, there was no significant difference in progression-free survival between the two drug groups. However, this study has several limitations as of the nature of retrospective design; our data suggest that gefitinib and erlotinib might have almost equal efficacy for patients with EGFR-wt NSCLC, as is the case for patients with EGFR-mt tumors, although erlotinib appears to have higher toxicity than gefitinib at each approved dose.