Ruminococcus albus was incubated with isolated alfalfa cell wall material for 72 h in batch culture. Cellulose in the cell walls was digested to a somewhat greater extent (88%) than were the fermentable sugars of the hemicellulose fraction (62 – 76%). The digestibility of the total insoluble alfalfa cell wall, including lignin but not material solubilized during heat sterilization, was 66%. A cellulase, α-arabinosidase and xylanase were partially purified from the concentrated supernatant of R. albus cultures and a purified polygalacturonase was obtained from the fungus Verticillium. Of the enzymes tested, the most effective in digesting cell walls was the polygalacturonase. In addition, when mixed with α-arabinosidase, the amount digested exceeded the sum of the materials digested by the two enzymes separately.