SUMMARYAllomyces arbusculahas a rather wide geographic distribution, having been found in the United States, Mexico, the West Indies, Costa Rica, Brazil, Argentina, China, and South Africa. Isolates from the various localities appear to be very constant in the characters of their resistant sporangia and gametangia.Allomyces javanicusis reported for the first time in the western hemisphere, from collections in Mexico, Texas, and the southwestern United States.Allomyces cystogenusis reported for the first time from North America, from Arizona, andRozella Allomycis, a parasite ofA. arbuscula, has been found to occur in Argentina and Brazil.It is suggested that the two long cycled species,A. arbusculaandA. javanicus, can be very conveniently separated on the basis of resistant sporangial size.