Thirty-two patients with small cell carcinoma of the lung were given chest radiotherapy to progressive intrathoracic tumor after failing chemotherapy. Two-thirds of these patients received split-course treatment at a dose of 4000 rad in 10 fractions. Sixteen of 25 evaluable patients (64%) had an objective response, but only five responders did not progress within the port during life. Median time to local progression was 16 weeks. Two patients, one of whom was given concurrent chemotherapy, survived greater than 18 months, and one is free of disease at 31+ months. Short-term palliation of chest disease and occasional long-term survival are possible with this regimen, although most patients will die with systemic disease within several months. Small cell carcinoma of the lung is less responsive to irradiation as second-line therapy than as initial therapy, but doses of greater than or equal to 4000 rad can offer symptomatic relief in many cases and, rarely, survival beyond 18 months.