The artificial transmission of besnoitiosis from chronically infected cattle to rabbits and cattle is recorded. The infective inoculum consisted of a suspension of heavily parasitized cyst-bearing skin and other tissues in saline or Hanks' solution. Large numbers of cyst organisms were present in the inoculum which were apparently responsible for the transmission. Blood from the chronically infected cattle used as donors of the cyst-bearing tissues was not infective. Cattle were, in turn, infected with blood obtained from the rabbits when they reacted to infection with cyst organisms, thus fulfilling Koch's postulates. Rabbits developed typical symptoms of besnoitiosis as described for infection with proliferative organisms. Cattle developed a mild form of the disease as described for the majority of animals infected with proliferative forms. The reason for this is obscure, but it is pointed out that the results seen after artificial infection are in agreement with observations made in nature. On the strength of these findings it is suggested that clinically apparent, chronically infected cattle probably serve as reservoirs of bovine besnoitiosis, and bloodsucking arthropods act as mechanical vectors. The six strains of B. besnoiti isolated in this experiment were immune- genically indistinguishable from two strains isolated previously.