Webster and Clow1 and Kanazawa2 reported the first success in cultivating rabies virus. The former accomplished this with a medium consisting of Tyrode solution containing normal monkey serum and minced mouse embryo brain, while the latter propagated the virus in Tyrode solution in the presence of rabbit embryo brain tissue, but without the addition of serum.We wish to report our confirmation of the observations of Webster and Clow, since by the procedure which they describe, we have been able to carry the virus through 16 subcultures. Material from the final culture has proved infectious for Swiss mice in dilution of 102. In addition a series of passages carried out on the same medium, but with an equivalent amount of normal rabbit serum in place of normal monkey serum yielded results which were similar in all respects to those obtained with normal monkey serum.Attempts to propagate the virus on media containing a larger ratio of serum to Tyrode and considerably smaller amounts of tissue proved unsuccess...