investigate action of ethanol on histamine release from rat peritoneal mast cells, we compared the inhibitory effect of ethanol with those of calcium antagonists in mechanism of between ATP and compound 48/80-induced histamine release. Ethanol dose-dependently inhibited 100 ${mu}{ extrm}{m}$ ATP-induced histamine release, whereas did not inhibit 1 $mu extrm{g}$/ml compound 48/80-induced histamine release. Verapamil, TMB-8 and EGTA dose-dependently inhibited ATP-induced histamine release, but did not inhibit compound 48/80-induced histamine release. Such an inhibitory effect of calcium antagonist was similar to that of ethanol. These results suggest that the inhibitory effect of ethanol on histamine release from rat peritoneal mast cells is mediated via disturbance of calcium mobilization..