Immunological survey of 3 patients with proved rabies encephalitis shows three interesting facts. 1) An IgM local synthesis, sometimes proportionally higher than IgG local synthesis, is observed in 8 CSF (among 13 investigated) and detected early, during the first week of the disease for 2 patients. 2) A relative poor IgG response is noted; this response is absent in one and decreasing in the 2 others patients despite their progressive aggravation. 3) A very little elevation of blood nucleic antibodies is detected in 5 CSF only. This very poor synthesis of antinucleic IgG contrast with their common increase in viral encephalitis. Thus, a viral immunosuppression may be discussed in rabies encephalitis, which may contribute to the lethal prognosis.