Although gefitinib is known to possess an effect inducing apoptosis against lung cancer, it is not clear how clinically effective it is in this regard in patients with lung cancer. Therefore, we tried to reduce its administration from every to every other day in a 73-year-old woman in good condition over 5 years after the recurrence of lung cancer. As a result, her CEA serum level then commenced to increase to the abnormal range within a month. Apoptosis induced by gefitinib was thought not sufficient to kill all lung cancer cells even though well controlled by it for a long period.