The authors present the results of a non randomized study of 33 patients suffering from small cell carcinoma of the lung. After a similar course of monthly chemo-therapy (Endoxan Oncovin, Natulan, CCNU) and mediastinal irradiation in a dose of 30 grays in 10 fractions over two weeks, 14 patients were given adjuvant cerebral irradiation, the 19 others made up the control group (30 grays to the brain overall in 10 fractions over two weeks). With a minimum follow up for 12 months, 42% of the control group had evidence of cerebral secondaries, as opposed to none in the irradiated group with any neurological signs whatsoever. The indisputable efficacy of adjuvant cerebral irradiation contrasts with the absence of any significant improvement in survival time : 2 patients are alive and in complete remission, 1 in each group, while the mean survival was 12.3 and 11.7 months respectively. This is explained by the continued occurrence of extra-cerebral metastatic deposits such as the liver or mediastinum where the efficacy of systemic therapy remains uncertain. The therapeutic approach is currently orientated in two directions : - to raise the dose delivered to the mediastinum even if it appears radiologically normal. - to continue research into new chemo-therapeutic combinations more specifically active at the hepatic level.