Abstract-A comparative study was carried out on the effects of a soluble derivative of baicalein, disodium baicalein 6-phosphate (BPS) and disodium cromoglycate (DSCG) on the immediate type allergic reactions.BPS not only inhibited reaginic antibody mediated reactions including antigen-induced mediator release from monkey lung, homologous PCA in rats, and reaginic antibody-mediated degranulation of mast cell, but also non-reaginic antibody-mediated reactions such as mediator release from guinea pig lung sensitized with ovalbumin and that from human lung caused by anti IgE. The agent, however, did not affect the mediator release from lung of rats sensitized with dinitrophynylated ascaris extract plus Bordetella pertussis. On the other hand, DSCG showed characteristic properties as an inhibitor of reaginic antibody-mediated reaction.It is thus assumed that the functional site of reaginic antibody is well fixed with DSCG at a definite distance between the two-chromone-nuclei while that of IgG is readily fixed with the two molecules of baicalein or BPS.Baicalein and baicalin are flavones contained in the radix of Scutellaria baicalensis GEORGI (Woogon), which from ancient times has often been used in Chinese medicine as a remedy for allergic diseases and inflammation. We (1-5) have already reported the anti allergic activity of baicalein and its derivatives, and these substances also have a potent protective action against active and passive anaphylaxis. These agents were also found to inhibit reagin-mediated reaction as well as disodium cromoglycate (DSCG). DSCG does inhibit reagin-mediated reaction with a fairly high specificity (6-12), however, inhibits not at all or only slightly non-reaginic antibody-mediated reactions (7-12) and the mediator release by specific antigen from the leucocytes of allergic patient (13).From the viewpoint of chemical structures, baicalein is a monochromone derivative while DSCG is a symmetric dichromone derivative, as shown in Fig. 1