There was limited knowledge about drug-induced ILD(DILD), when safety reports of acute ILD-type events in gefitinib-treated patients appeared in Japan. There is a need to better understand DILD including event incidence on different treatments and risk factors for developing DILD. Some studies using recent advances in imaging, molecular examination, and pathology are designed and conducted by an independent academic team to define the risk and increase understanding of ILD of various agents in a postmarketing surveillance. These studies may help to shed light on the underlying mechanisms of DILD and appropriate strategies for such events.