A total of 306 patients with small cell lung cancer (SCLC) were randomized to receive chemotherapy in a sequential or alternating mode. Sequential chemotherapy consisted of eight cycles of cyclophosphamide, Adriamycin (doxorubicin), and vincristine (CAV) and alternating chemotherapy consisted of three cycles (1, 3, 5) of etoposide, vindesine, and ifosfamide (EVI); three cycles (2, 4, 6) of cisplatin, Adriamycin, and vincristine (PAV); and two cycles (7, 8) of cyclophosphamide, methotrexate, and CCNU (CMC). Responsive patients received prophylactic cranial irradiation after three cycles and chest irradiation after eight cycles of chemotherapy. No maintenance therapy was applied to patients achieving complete remission. Minimum follow-up was 2 years. Of the 302 patients evaluable, overall response rate was 59% in the sequential arm and 70% in the alternating arm. Patients treated with CAV had a complete response rate of 21% in contrast to 36% for those receiving alternating therapy. The median survival for all patients was 9.8 versus 11.3 months, for limited disease 11.1 versus 13.4 months, and for extensive disease 8.9 versus 9.9 months, all in favor of the alternating treatment. Two-year survival rate for all patients was 6% versus 9%, for limited disease 11% versus 14%, and for extensive disease 3% versus 6%, all preferring the alternating treatment mode. Progression-free survival demonstrated a strong correlation to the extent of response irrespective of the treatment regimen applied. Toxicity included 11 lethal and 8 life-threatening complications with a higher frequency in the alternating treatment arm. These results suggest that alternating treatment of SCLC with different drug combinations is more effective than sequential application of CAV.