In testing the skin for conditions of atopic hypersensitiveness, the clinician, whether he employs the scratch or intradermal method, is often confronted with numerous difficulties. He is especially handicapped in the testing of infants and small children, where the patient's coöperation is usually lacking, and the danger of constitutional reactions is always imminent. At times, an irritable skin, or the presence of dermographia or a diffuse eczema, erythema, or lichenification, seriously interferes with the performance and interpretation of the tests. It is in the hope of avoiding some of these difficulties that the method to be presently described is offered, as an alternative procedure to the direct testing of these types of cases. In 1921, Prausnitz and Küster (1) first demonstrated passive transfer of local sensitivity by injecting into the skin of a normal individual the serum of a fish-sensitive case, and subsequently eliciting a specific positive skin test for fish at this site.