In small-cell lung cancer, the optimal combination of chemotherapy and radiotherapy is not clearly established. To assess the value of delayed thoracic radiotherapy, we performed a randomized clinical trial in 53 complete responder patients after eight courses of chemotherapy. Twenty-seven patients received a mean of 46.5 Gy-equivalent of radiotherapy and 26 patients received no treatment until relapse. No patient dropped out of the study. Median survival time from radiotherapy randomization was 316 days in the radiotherapy group and 496 days in the no radiotherapy group. No difference was observed in survival between the two groups (p = 0.66, log-rank test) perhaps because of the small sample size. In fact, this delayed thoracic radiotherapy seemed to worsen the outcome of complete responders with small-cell lung cancer and should be avoided.