Encouraged by results of experiments reported previously on guinea pigs (1) with experimental meningococcus antitoxin (2), the work was extended to include the monkey. The writer found, as did Flexner (3) many years previously, that acute and fatal cerebrospinal meningitis can be produced in the monkey by intraspinal inoculations with virulent meningococci and that results are fairly consistent in susceptible animals when the cultures are recently isolated and the animals are about of the same weight and age. It was found by the writer, however, that the susceptibility of this animal toward the meningococcus varied considerably, depending not only upon age and weight but also upon individual natural resistance. The findings of Flexner were also corroborated to the effect that any infection in the monkey with this organism, by way of the spinal canal, which results fatally, has a very acute onset and is of short duration, and, that if the first inoculation does not produce typical symptoms, the second or third, made shortly afterwards, will probably do so.