Between January 1985 and August 1991, 159 patients with small cell lung cancer received first-line chemotherapy and 123 (77%) were responders. Of these, 88 relapsed, the remainder having died of other or unknown diseases or being alive without carrying cancer. The relapsed patients were examined to evaluate the outcome of the treatment for relapsed small cell lung cancer and to identify the factors that would contribute to the response rates and the survival durations. Forty-eight of 88 relapsed patients received second-line chemotherapy. Of the 48, 3 were evaluated as showing a complete response, 13 as partial response, 9 as no change, 15 as progressive disease and 8 as not evaluable. The response rate was 33% (95% confidence interval 20.4-48.4%). The median survival time was 146 days. The duration and rate of response in first-line chemotherapy affected the response rates of the second-line chemotherapy, but without statistical significance (P = 0.058 and 0.067 respectively). Increased response duration, time off chemotherapy and previous response to first-line chemotherapy all had a positive effect on the survival times (P < 0.01). Relapsed small cell lung cancer still shows a response to second-line chemotherapy without lessening survival time, and thus clinical trials of new drugs or combination chemotherapeutic regimens for relapsed small cell lung cancer cases would be reasonably justified. Randomized comparative studies are warranted for determining the benefits of second-line chemotherapy for relapsed small cell lung cancer cases.