For several years, chemotherapy has been the only treatment of small-cell carcinoma of the lung, but radiotherapy is increasingly used for its local effect in various ways. Irradiation of the chest alternating or concomitant with chemotherapy has become a basic principle in localized forms of the disease and may perhaps be useful in its diffuse forms. The so-called "prophylactic" brain irradiation is routinely performed, even though its beneficial effect on survival has not yet been demonstrated. As for extensive irradiation, it is still under study. Radiotherapy therefore plays an important role which, added to that of chemotherapy, should result in an improvement of long-term survival in patients with small-cell carcinoma of the lung.