Water-soluble crude polysaccharide (CAP-0) obtained from the Capsici Fructus(the fruits of Capsium annuum L.) showed a potent anti-complementary activity. The anti-complementary activity did not change by pronase digestion of CAP-0, but decreased by the periodate oxidation. CAP-0 was fractionated into four polysaccharide fractions, CAP-1, 2, 3 and 4, by the addition of cetyltrimethylammonium bromide. CAP-1, showing the highest anti-complementary activity, was refractioned by anion-exchange chromatography to give three major fractions(CAP-1-III, IV and V). CAP-1-III was shown to have low anti-complementary activity, but CAP-1-IV and V had high activity. CAP-1-III and IV were purified on Sephadex G-100 to give each two fractions(CAP-1-IIIa and IIIb, CAP-1-IVa and IVb), respectively. From the results of gel filtration and electrophoresis, these four fractions and CAP-1-V were found to be homogeneous polysaccharides. High molecular polysaccharies(M.W. CAP-1-IIIa 70,000, IVa 195,000, V 140,000) showed relatively higher anti-complementary activity than low molecular polysaccharides(CAP-1-IIIb and IVb).