Defaunated sheep offered lucerne hay or dried red clover were used to study digestion in the stomach of dietary organic matter, plant cell wall constituents, and plant cell contents. Digestion in that section of the tract was, for dietary organic matter, 50 % with lucerne and 60% with red clover, for plant cell contents 65–70% with both diets, and for plant cell wall constituents 30% with lucerne and 60 % with red clover. Estimates of growth of rumen bacteria in these sheep indicated that about 32 g of bacterial organic matter and 23 g of bacterial crude protein were synthesized in the rumen for each 100 g of plant organic matter digested. Comparisons of apparent digestion in the stomach and intestines were made between the defaunated sheep and the same sheep carrying a normal population of rumen microorganisms. Levels of rumen ammonia were lower in the absence of protozoa. However, only small differences were observed in the flow of digesta along the tract and in the apparent digestion of organic matter and nitrogen in both the stomach and intestines as a result of defamation. Hence it is suggested that data on the digestion of forages obtained with defaunated sheep can be applied to sheep with rumen protozoa.