The purposes of this study are:

• To estimate the relative risk of ILD in advanced/recurrence NSCLC patients treated with gefitinib as compared to other chemotherapy treatment, and to assess the risk factors for ILD in advanced/recurrence NSCLC patients undergoing treatment
• To provide an estimate of the incidence of ILD in a group of advanced/recurrence NSCLC patients undergoing treatment

Inclusion Criteria:

• Advanced/recurrence NSCLC patients who have had one or more chemotherapy regimens.
• Patients who are to be treated with gefitinib or chemotherapy
• Cohort: All advanced/recurrence NSCLC patients participating in this post-marketing clinical study

Exclusion Criteria:

• Patients judged by the investigator(s) to have ILD (provisional cases) among those registered in the cohort OR Randomly selected patients without ILD (controls) for each provisional case
• Case-control study: Patients enrolled in the case-control study; all consenting patients with ILD as cases and approximately 4 times as many consenting patients without ILD as controls randomly selected from the cohort

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