The use of prophylactic cranial irradiation in limited stage small cell lung cancer remains controversial. Prospective trials have demonstrated that PCI can reduce central nervous system relapse rates, but the impact on survival remains questionable except for the possible evidence of a beneficial effect for long term survivors. With higher rates of thoracic control now obtainable with hyperfractionated radiation and concomitant chemotherapy, it becomes important to analyze the benefit of PCI in that setting. Before 1982, we included PCI in the management of all patients with limited stage small cell lung cancer; thereafter, we discontinued its use. This report compares the outcome of the two treatment approaches and addresses the role of PCI among patients who achieve durable local control. There were 36 limited stage small cell lung cancer patients treated with PCI from 1979-1982 and 26 patients treated without PCI from 1985-1989. Induction chemotherapy was followed in both groups by thoracic irradiation (45 Gy). The PCI patients received 30 Gy to the whole brain in 10 fractions. Both groups received maintenance chemotherapy. Of complete responders, brain failure was the first failure in 18% (4/22) of PCI (+) versus 45% (10/22) of PCI (-) (p = .04). Survival at 2 years was 42% for PCI (+) versus 13% for PCI (-) (p less than .05). When the analysis was limited to those patients permanently controlled in the thorax; there were 25% (4/16) brain failures PCI (+) versus 70% (7/10) PCI (-) (p = .03). For this same subset the 2-year survival was 56% PCI (+) versus 14% PCI (-) (p less than .05). There were no 5 year survivors without PCI compared to 38% (6/16) with PCI. These data suggest that PCI appears to be effective in enhancing survival of patients who achieve durable thoracic control. Prospective trials are necessary to evaluate the use of PCI combined with therapeutic regimens with a documented ability to achieve high rates of sustained control of thoracic disease.