This paper embodies the experience gained in the study and treatment of 260 cases of angioneurotic edema and urticaria. No distinction is made between these two disorders. It is assumed that they are the same process, involving in the case of urticaria the superficial layers of the skin, and in angioneurotic edema the subcutaneous tissues. In some instances other tissues may be involved also, as in the type of epilepsy due to allergic reaction. The point of view from which these observations are made is that in these cases the disorder is allergic, and that in every case there is a definite etiology. This etiologic factor is always the absorption of some foreign protein by a sensitive individual, just as in hay-fever and bronchial asthma. Successful treatment in hay-fever and bronchial asthma depends on first determining what foreign protein or proteins are responsible for the reaction. The offending substance is