Comparative studies of alternating non-cross resistant chemotherapy, A.V.N.-D.V.C. (ACNU + VCR + PCZ-ADM + VCR + CPA) was carried out on 19 patients with small cell lung cancer. A.V.N. (A. V.F.) therapy on 45 patients and D.V.C. therapy on 19 patients were used as historical control, respectively. A.V.N. (A.V.F.) therapy was composed of ACNU (2.5 mg/kg, day 1), VCR (0.02 mg/kg, once every week) and PCZ (1 mg/kg, daily) (or FT-207 (15 mg/kg, daily], and duration of one course was 6 to 8 weeks. D.V.C. therapy was composed of ADM (1 mg/kg, day 1) VCR (0.02 mg/kg, days 1 and 5) and CPA (2 mg/kg, days 1 to 5), and repeated every 4 weeks. A.V.N.-D.V.C. therapy was done by a timely alternation of one course of A.V.N. and two course of D.V.C. Reduction rate of tumor size was 84% in A.V.N.-D.V.C. therapy, 62% in A.V.N. (A.V.F.) therapy and 26% in D.V.C. therapy, respectively. Median survival time was 13 months on A.V.N.-D.N.C. therapy, 8.5 months and A.V.N. (A. V.F.) therapy and 4 months on D.V.C. therapy. Significant prolongation of median survival time was obtained in A.V.N.-D.V.C. therapy in comparison with that of historical controls. Major toxicity in A.V.N.-D.V.C. therapy was slight bone marrow suppression.