The findings concerning the protein pattern of cerebrospinal fluid (CSF) samples from 15 patients with meningo-radiculo-myelitis probably related to virus infection (MMR) are reported. Protein fractions were separated by paper electrophoresis. The results obtained were discussed comparatively with those obtained for CSF samples from 10 cases of polyradiculoneuritis (PRN). Total protein concentration was slightly increased in most of MMR cases. The changes found in the protein pattern were similar in both groups of patients but they were more conspicuous among those of MMR group. Moderate increase of gamma globulin relative concentration was the main change observed in most of MMR cases. The meaning of changes observed were discussed.