1. Twenty germ-free and twenty conventional male Fischer 344 rats, 3 months old, were fed ad lib. diets based either on normal or on amylomaize starch for 1 month. The absorption rate of sodium taurocholate. 25 mmol/l, was determined in vivo in jejunal or ileal segments. Each determination included five rats.
2. Jejunal absorption rate was not modified either by the amylomaize-based diet or by the digestive microflora.
3. Ileal absorption rate was slightly higher in germ-free than in conventional rats.
4. Ileal absorption rate was largely increased by the amylomaize-based diet. This increase was slightly larger in germ-free rats than in conventional rats.
5. It is suggested that dietary amylomaize starch has an action on the active absorption process of bile acid.