1. Experiments are reported on the use of poliomyelitis virus neutralized by specific antiserum as an agent to induce active immunity against the experimental disease in monkeys.
2. The results indicate that protection can be conferred upon a certain number of the treated animals.
3. The neutralized material gave rise in no instance to symptoms of disease in the treated monkeys.
4. Active poliomyelitis virus, suitably neutralized by admixture with convalescent serum, was without pathogenic effect when given by repeated nasal instillations.