The distribution and specific activities of polysaccharide-degrading enzymes were monitored during the postprandial period in the liquid-associated bacteria (LAB), liquid-associated protozoa (LAP), and solid-associated microbes (SBFP) isolated from ruminal contents of cattle fed a high-cereal diet. Polysaccharide depolymerase activities were highest in the SBFP and the LAP populations. The postprandial variations in the specific activity of amylase were similar within the subpopulations. However, carboxymethylcellulase and xylanase activities increased in the first 5 h after feeding in the LAP, but were highest at the end of the postprandial period in the SBFP. Glycosidases involved in the fermentation of soluble carbohydrates increased significantly immediately after feeding in the liquid-associated microbes. Beta-D-Glucosidase and beta-D-xylosidase were most active in the SBFP and were maximal 23 h after feeding. The activities of the plant cell wall polysaccharide-degrading enzymes and glycosidases in the SBFP were inversely related to ruminal pH; however, the activity of enzymes in the liquid-associated populations were highest in the immediate post-feed period when ruminal pH was lowest.