We studied the probability of survival of subacute sclerosing panencephalitis (SSPE) patients prognostically stratified into rapidly and slowly developing SSPE, nontreatment, and inosiplex-treated groups. Based on life table analysis, survival did not differ between treated and untreated patients with rapidly developing SSPE. The cumulative survival rates were significantly (p < 0.05) higher and the mortality rate slgnificantly lower in the slowly developing inosiplex-treated group.