During the past five years, 15 patients with subacute sclerosing panencephalitis (SSPE) were treated with inosiplex. Using a disability index specifically designed for the disease, this study monitored the course of SSPE in each patient before and during inosiplex therapy. Posttreatment follow-up ranged from 2 to 144 months. Inosiplex had an apparently beneficial effect on morbidity and mortality in 10 of the 15 patients tested. Eight improved immediately after treatment, 2 had a delayed improvement, and 1 patient stabilized. Four patients followed a typical course for SSPE and died a mean 9 months after onset. Treatment was not associated with adverse reactions. Due to its low risk-benefit ratio, inosiplex is recommended for continuous use in SSPE even after extended remissions.