The neutralization test has proven a highly important aid in the recognition and epidemiological study of numerous virus diseases. In lymphogranuloma venereum as well, this test should be distinctly valuable, especially in those cases where it is not possible or practicable to perform the Frei test or where there is anergy or a doubtful skin reaction. Unfortunately, however, the literature on this subject, as in many of the experimental phases of this disease, is contradictory. Levaditi and his coworkers,1 to whom we owe much of the pioneer work in lymphogranuloma venereum, first reported successful neutralization experiments using the monkey as test animal in 1931. In the following year, they2 obtained positive results with the mouse. Also in 1932, Findlay3 successfully employed this test and by means of it, was able to establish the identity of climatic bubo and lymphogranuloma venereum. Wassin, in 1935, not only obtained positive results by means of the intracerebral neutralization test in mice, but devised a new intradermal test in the guinea pig. Miyagawa6 and his coworkers confirmed these observations. More