The nylon bag technique was used with 2 fistulated steers to determine the effect semi-purified enzymes might have upon the digestibilities of the various components of low quality roughage. After a 10 day equilibrating period to each treatment, finely ground roughage was suspended in the rumen via the rumen-fistula in 19 nylon bags per steer, containing 10 grams per bag. Duplicate bags were removed from each animal every 24 hours. The samples were washed to remove rumen liquor, dried and subjected to accepted proximate analyses. Pectinase, XC 597, HT Protease, Fungal Protease or Fungal Amylase were introduced via the fistula plug daily in gelatin capsules at approximately 0.05% of the diet. An empty gelatin capsule was used in the case of the control. Roughage of poor quality was fed during these trials. At the levels fed XC-597 significantly (p< 05) reduced the digestibility of dry matter whereas Fungal Protease resulted in a significant increase. Fungal Protease and Fungal Amylase increased, while XC-597 and HT Proteolytic decreased the digestibility of the ether extracts. XC-597 significantly decreased crude fiber and cellulose digestibility. Fungal Protease increased digestibility of the cellulose above the HT Proteolytic and Fungal Amylase. There was no consistant trend in protein digestibility. The digestion of the ether extract portion of the ration proceeds at a more rapid rate than dry matter, crude fiber or cellulose and plateaus at about 48 hours.