IFN-alpha was detected in cerebrospinal fluid and/or sera from 7 of 8 patients with a progressive familial encephalopathy associated with calcifications of the basal ganglia and white matter alterations. The secretion of IFN-alpha was prolonged, as shown by its presence at different times between birth and 5 years, and was not associated with IFN-gamma. Virological investigations excluded various congenital infections. In only 2 patients, high levels of Epstein-Barr virus antibodies were observed, indicating the possibility of an abnormal response to viral infection rather than a congenital infection. Further investigations are required for characterization of the recessive autosomal trait of this syndrome and its relation to the IFN system.