The efficacy of oral inosiplex alone (group A) versus combined treatment of inosiplex (Isoprinosine) and intraventricular interferon-alpha2b (Intron A) (group B) in patients with subacute sclerosing panencephalitis (SSPE) was compared. One hundred and twenty-one patients who met the diagnostic criteria for subacute sclerosing panencephalitis and presented at stage 2 or less were randomized into group A or B. Data were analyzable on 67 patients who met the inclusion criteria and adhered to the protocol. The inosiplex dosage was 100 mg/kg/day to a maximum of 3 g/day, taken orally in three divided doses for 6 months. Interferon-alpha2b started with 100,000 U/m2 and escalated to 1,000,000 U/m2 over 5 inpatient days and then 1,000,000 U/m2 twice a week for 6 months. Neurologic status was rated by the Neurological Disability Index, Brief Assessment Examination, and stages. Kaplan-Meier survival rates were not statistically significant between group A and group B (log-rank test chi2 = .1374, P = .7109). In longitudinal morbidity analyses, regression results were fitted to three outcome measures: the Neurological Disability Index, the Brief Assessment Examination, and stage. Group medians of the estimated regression slopes were then compared using the Wilcoxon rank-sum test. There was no statistically significant difference between the two groups on any of these three measures. Morbidity comparisons of clinical classification of outcomes (improvement, stabilization, worsening after treatment stopped, deterioration) also showed no statistically significant difference between groups. There were no statistically significant differences between the two treatment groups on any efficacy measure. However, the observed rates of satisfactory outcome (stabilization, improvement) of 34% in group A and 35% in group B were higher than the spontaneous remission rates of 5 to 10% reported in the literature, suggesting that treatment was superior to no treatment.