1. A combination of poliomyelitis virus and specific human serum is effective for the production of active immunity.
2. For each gram of active virus given intradermally as an emulsion, 6 cc. of human immune serum, injected subcutaneously, was required in our experiments to protect a monkey from paralysis. Some degree of active immunity was induced.
3. Immunity, without symptom of the disease, was secured when the serum was given at the time of inoculation, or within 3 days preceding or following inoculation of the virus.
4. For the production of immunity, virus, preceded by serum administration, is probably less effective than when it is given simultaneously with, or before, the injection of serum.
5. The virus neutralization test is more sensitive than the direct intracerebral test for determining the production of immunity.