To provide the general profiles of efficacy and safety of erlotinib in Japanese patients with non-small cell lung cancer (NSCLC), we conducted an integrated analysis of two phase II studies (JO16565 and JO18396). The objective response rate was 28% (30/106 patients). The early partial response-in (PR-in) (at least a 30% decrease in the sum of diameters of target lesions, taking as reference the baseline sum diameters) within 30 days from start of treatment was observed in 70% of responding patients (21/30 patients). The early symptomatic improvement within 15 days from the start of treatment was observed in 77% of improving patients in Lung Cancer Subscale (LCS) (30/39 patients). In patients with stable disease (SD), a high improvement rate using LCS (65% [11/17 patients]) was observed, and the duration of improvement was positively correlated with that of SD. Therefore erlotinib was found to show promising symptomatic improvement not only in responding patients, but also in nonresponding patients with SD. Favorable dose reduction was considered to enable maintaining antitumor efficacy in patients who required dose reductions because of adverse events.