In a series of tests designed to illustrate immune reactions similar to those obtained in atopic disease, Wy-16,922 [2''-carbamoyl-3''-methoxyoxanilic acid ethyl ester] effectively inhibited reaginic-mediated immunologic reactions in the skin, lungs and mast cell of rats. It was devoid of immunosuppressant antimediator, anti-inflammatory, steroid or bronchodilator properties and acute toxicity. Although the mechanism of action of Wy-16,922 is unknown, it appears to limit the release (not the effects) of allergic mediators in a manner similar to that described for disodium cromoglycate.