Based upon the results of phase I study of irinotecan (CPT-11) combined with cisplatin (CDDP) on non-small cell lung cancer (NSCLC), a combination phase II study on NSCLC was carried out from Feb., 1992 to Sep., 1992. CPT-11 (60 mg/m2) and CDDP (80 mg/m2) were administered by i.v. drip infusion, with administration schedules of Days 1, 8, 15 and only Day 1, respectively. This therapy course was repeated every 4 weeks. Subjects were NSCLC patients of stage III B or IV disease. Those without prior chemotherapy (Group A) and those with prior therapy (Group B) were enrolled separately. Seventy patients were entered into Group A and 32 patients into Group B. One of the patients of Group A was ineligible. The characteristics of the eligible cases of Group A were: male/female, 51/18; median age, 61 years old; PS 0/1/2, 18/39/12; stage IIIB/IV, 26/43; and adeno/squamous/large, 51/15/3. Those of group B were: male/female, 20/12; median age, 62 years old; PS 0/1/2, 5/18/9; stage I/IIIB/IV, 1/7/24, adeno/squamous/large/ad-sq, 28/2/1/1. Thirty-three patients (47.8%) responded in Group A and B patients (25.0%) responded in Group B. Major adverse reactions (grade 3 or higher) of Group A/Group B were neutropenia (80.3%/73.3%), anemia (35.3%/34.4%), diarrhea (18.8%/28.1%) and nausea/vomiting (34.8%/34.4%). Median survival times for Group A and Group B were 308 and 295 days, respectively. CPT-11 in combination with CDDP is effective against NSCLC, suggesting that further studies are needed to determine the usefulness of this therapy.