ucb L140 (CHINOIN 1045) has been tested in various rat anaphylaxis systems. In models of passive cutaneous anaphylaxis (PCA), passive peritoneal anaphylaxis (PPA) and anaphylactic bronchospasms, ucb L140 appears to be more potent than sodium cromoglycate (DSCG). Upon oral administration, ucb L140 exhibits a marked inhibition of these anaphylactic reactions. Sensitized rat mast cells in vitro display a decreased Nippostrongylus-induced histamine release when treated with a concentration of ucb L140 three times smaller than DSCG. In PCA testing after intravenous administration of ucb L140 a cross-tachyphylaxis with DSCG was observed. These results suggest that the action of ucb L140 is similar to that of DSCG in inhibiting the release of allergic mediators from mast cells and therefore may present antiallergic activity.