The decoction of Rhei Rhizoma was divided into several fractions by the methods of extraction using methanol, membrane-permeability and HPLC. And the effects of the fractions on the contents of blood lipid in hyper-cholesterol rats and those on a pancreatic lipase were examined. The results were : 1. The fraction, which was soluble in methanol, of total and LDL-cholesterol in the blood of hyper-cholesterol rats significantly decreased the levels. 2. The decoction prepared from Rhei Rhizoma strongly inhibited the activity of the pancreatic lipase. And some fractions obtained from the decoction also had such an inhibitory effects. 3. The fraction, which decreased the lipid contents, also had an inhibitory effect on the pancreatic lipase. But the effect was very weak. These results suggested that the inhibitory effects of Rhei Rhizoma on the contents of blood lipid was induced not by the inhibitory component of the pancreatic lipase but by some other factors.