Irinotecan-induced interstitial lung disease (ILD) requires accurate diagnosis, followed by prompt and appropriate treatment. This study was conducted to compile information and imaging data to define the characteristics of irinotecan-induced ILD. Searches were performed on information collected for a drug reexamination application and on data from spontaneous safety reports submitted to Daiichi Sankyo Company, Limited. These database searches revealed 153 cases of serious ILD that occurred in association with irinotecan therapy, and which were reported as adverse drug reactions. Computed tomographic findings obtained after the onset of ILD were categorized based on four typical patterns. A total of 66 patients (including 15 for whom a relationship between death and serious ILD could not be excluded; incidence of serious ILD: 0.74%; death rate of ILD: 0.17%) were detected during the postmarketing surveillance along with 87 patients (22 deaths) that were identified from spontaneous reports. Within 16 weeks of starting treatment, 80.7% of the patients developed ILD. A total of 61.3% of the cases treated using steroids responded to the steroid therapy. These results indicate that there is no specific clinical or imaging feature associated with ILD related to irinotecan and that the prognosis of ILD related to irinotecan was poor in patients with preexisting ILD. The relative risk calculated for the association between preexisting ILD and death was 2.25 (P=0.29). During irinotecan treatments, patients need to be carefully observed for symptoms, especially at 16 weeks after starting treatment. In addition, when patients are receiving this type of therapy, they also need to undergo chest imaging studies.