Mechanism of the antiallergic action of 6-methyl-N-(1H-tetrazol-5-yl)-2-pyridinecarboxamide (TA-5707F) was studied using the water-soluble sodium salt (TA-5707). 1) TA-5707 administered p.o. at the dose ca. 3 times the ID50 for the PCA reaction did not inhibit capillary dye leakage induced on the rat skin by intracutaneous injection of histamine, serotonin, bradykinin and leukotriene D4 (LTD4). 2) TA-5707, at concentrations above 10(-7) M, inhibited antigen-induced histamine release and dye leakage in the rat peritoneal cavity (passive peritoneal anaphylaxis). 3) TA-5707 inhibited both anaphylactic and compound 48/80-induced histamine release from the rat peritoneal mast cells, the IC50 being ca. 10(-5) M in both cases. It was concluded that TA-5707F exerts its antiallergic action by inhibiting the release of chemical mediators from sensitized cells.