Chronic urticaria, as well as atopic dermatitis, asthma, and allergic rhinitis is a representative disease mediated by IgE. Mast cells and basophils were previously known as main effector cells in chronic urticaria. However, recent studies are paying their attention to eosinophils and their roles in producing tissue factors in chronic urticaria . The role of Eosinophil Cationic Protein (ECP) is well documented in atopic dermatitis, asthma and allergic rhinitis patients [2,3]. ECP is a cytotoxic agent secreted by activated eosinophils during allergic or inflammatory process and has been examined in various allergic disorders as an activation marker. However, there have been few reports about serum ECP and its clinical significance in patients with chronic urticaria. With this background, we evaluate serum ECP and total IgE as a severity index in chronic urticaria patients.