Abstract It is generally conceded that the gonococcus is a very refractory organism to cultivate artificially, especially in liquid media. When growth does occur in the latter, even in a medium well fortified with any one of the serous human body fluids, the results are extremely uncertain, particularly in amount and duration of proliferation. This lack of adaptability to artificial cultural conditions perhaps accounts for the comparatively little work that has been reported in the literature referring to systematic studies on germ-free filtrates of the gonococcus and methods suited to their preparation and evaluation. The inherent tendency of cultures of the gonococcus to autolyze offers another obstacle to the analysis of such filtrates, as found by McClintock and Clark (1) and others. The work presented in this paper covers the preparation and testing of a toxic filtrate from liquid culture of the gonococcus which followed a request from Dr. B. C. Corbus of Chicago for a bouillon filtrate of the gonococcus in the nature of an “antivirus.”