A review of CT scans of 7,081 patients demonstrated calcifications of the basal ganglia in 53. The calcifications were evident in the skull roentgenograms of only 4 patients out of 40 in whom both CT scans and plain roentgenograms were available, demonstrating the superior resolution of this new method. Seventy-five percent of the patients were older than 50 years of age. Of the younger patients, 5 had had prior cranial irradiation; 1 had received cranial irradiation and intrathecal methotrexate therapy for meningeal leukemia; and 2 others had deep-seated arteriovenous malformations. Serum concentrations of calcium and phosphorus were normal in all 46 patients in whom they were measured. We conclude that the detection of small calcifications of the basal ganglia in persons above 50 years of age is infrequently associated with either clinical signs of basal ganglia dysfunction or calcium and phosphorus abnormalities. Calcium deposition in these patients may be related to vascular changes associated with aging. In younger patients a specific pathogenetic factor or underlying process is infrequently found.