A 74-year old man was treated with first-cycle chemotherapy of paclitaxel (70 mg/m2=110 mg day 1, 8, 15) and carboplatin (AUC5=500 mg day 1) for lung cancer (c-T3N2M0, stage III A). On day 6 abdominal pain appeared, while on day 7 abdominal CT showed a perforation of the digestive tract. Thirty-three hours after the onset he underwent Hartmann operation during which we recognized a perforation 1.7 cm in size in the rectum. Although the cause of the perforation was unknown from the pathological findings, anticancer agents were suspected to be involved. Perforation should be taken into consideration in connection with acute abdominal disease after chemotherapy.