Two media proposed for the isolation of cellulolytic rumen bacteria were investigated. The inorganic medium containing rumen fluid gave greater total counts, greater cellulolytic counts, and a greater variety of morphological forms of cellulolytic rumen bacteria than the rich organic medium containing no rumen fluid. Cellulolytic bacteria were isolated in the inorganic medium which could not be subcultured in the rich organic medium. No cellulolytic bacteria were isolated in the rich organic medium which could not be subcultured in the inorganic medium containing rumen fluid. On the basis of the data obtained, it was concluded that under the conditions of the investigation the inorganic medium containing rumen fluid is superior to the rich organic medium for the culturing of cellulolytic rumen bacteria and for the culturing of the predominating fora of the rumen. / M.S.