Three children with subacute sclerosing panencephalitis (SSPE) were treated with alpha-interferon. Medication was administered via an Ommaya reservoir into the cerebral ventricular system over a period of 13 to 24 months in increasing amounts up to 1.0 x 10(6) IU twice weekly. Mild clinical improvement in two children and a stable course in the third were associated with improvement of electroencephalographic recordings in all patients and a decrease in antimeasles antibodies in the cerebrospinal fluid of two. The small number of patients does not enable us to determine whether this course was the natural history of SSPE in our patients or whether it was induced by treatment, yet it seems that intraventricular interferon treatment can modify the course of SSPE.