Fifty-five patients with small cell lung cancer underwent computerized cranial tomography (CCT) and a complete neurologic examination as part of their staging work-up. Fifteen patients (27%) had evidence of brain metastases detected by CCT at the time of diagnosis. Eleven of these 15 patients had new focal abnormalities upon neurologic examination. Of the 44 patients who had no new focal abnormalities upon neurologic examination, four (9%) had CCT findings consistent with brain metastases, and, in three of these patients, the central nervous system was the only site of metastatic disease. Thus, through the use of CCT as a routine procedure in the staging of small cell lung cancer, three patients whose tumors would otherwise have been classified as limited-stage were found to have extensive-stage disease.