In several test model systems using spontaneous metastasizing experimental tumours, convincing data indicate the importance of the tumour burden left after surgery for the efficacy of the combination of surgery and chemotherapy. Early removal of the primary tumour by radical surgery for cure seems to improve the conditions for chemotherapy. Since 1979, in nine different departments of thoracic surgery, patients with small-cell carcinoma of the lung (SCCL) have been randomized after surgery for cure to receive a new sequential intermittent polychemotherapy (sq.CT) of 3 different alternating drug combinations given intermittently over 1 year, or one 4-drug combination chemotherapy (CT) given intermittently over 3 years. The calculation of their life table curves at 1 August 1984 indicated an improvement in the 4-year survival rate of 23 patients receiving sq.CT to about 50%, compared with a survival rate of about 30% for 29 patients receiving CT. The number of patients is still too small for firm conclusions to be drawn, but it is concluded that surgery for SCCL seems to be an advisable measure for the efficacy of aggressive intermittent long-term polychemotherapy. However, this can only be proved in large cooperative studies.