The water extract of Sophorae radix was tested for its preventive effects against cardiovascular anaphylaxis elicited in experimental animals. In actively sensitized pithed rats, the extract partially protected the animals from death resulting from antigen challenge. Of the cardiovascular changes observed during the anaphylaxis in the pithed animals, the initial pressor response was significantly attenuated by the extract. The extract also improved anaphylactic cardiac dysfunction in passively sensitized isolated guinea hearts: improvement was noted in the contractility, arrhythmic duration and lactate dehydrogenase elevation. The perfusion pressure change to antigen challenge was not altered by the extract in passively sensitized isolated mesenteric artery preparations. The extract however significantly inhibited homologous passive cutaneous anaphylaxis responses in rats. When examined in isolated guinea pig tracheal muscle, the extract did not influence at reasonable concentrations on the contraction elicited by three major anaphylactic mediators, histamine, leukotriene D4 and serotonin. These results suggest that the water extract of Sophorae radix possesses anti-anaphylactic effect in cardiovascular system, primarily acting on the heart not the peripheral resistance vessels.