Segment membranes from 4 citrus species selected from 4 sections were treated with water to obtain polysaccharides containing pectin. The extracts, which inhibited pancreatic lipase activity in a concentration-dependent manner, were divided into high molecular weight fractions [molecular weight (M.W.) >300,000], which inhibited the activity strongly, and low molecular weight fractions (M.W. <300,000), which did not show such strong inhibition. The high molecular weight fractions were composed mainly of a characteristic sugar of pectin, namely, galacturonic acid. A galacturonic acid-rich fraction purified by anion exchange chromatography from a water extract also strongly inhibited the activity. The inhibitory activity of the high molecular weight fraction was much stronger than that of commercial citrus pectin. The results suggest that pectin from segment membranes of citrus fruits might be useful as a functional food, especially as a fat-reducing material.