In a group of 37 children with SSPE serum protein and cerebrospinal fluid electrophoresis was done (in 34 and 25 cases respectively) determining immunoglobulins in the serum and cerebrospinal fluid in all 37 cases. The obtained results demonstrated a lack of correlation between the changes observed in the serum and cerebrospinal fluid. The most frequent change in the serum was a rise in alpha 2 globulin level (85%) and reduced IgA level (58%), while in the cerebrospinal fluid a rise in gamma globulins (92% of cases) and IgG (100%) was observed most frequently. A comparison of these results with past history of measles, with the clinical course of SSPE and with the survival time of the children showed no correlations. Measles antibodies were determined in the serum and cerebrospinal fluid in 37 children, and the determinations, were repeated several times in the serum of all children and in the cerebrospinal fluid of 9 children. Measles antibodies were found in the serum in all children and in the cerebrospinal fluid in 21 children (57%). The highest titres of antibodies above 1:32 in the cerebrospinal fluid were demonstrated in children with measles at the age up to 2 years. The prognosis was worst in children with acute onset of the disease preceded frequently by cranial injury or infection, with a high serum antibody level and absence of antibody in the cerebrospinal fluid.