Chronic urticaria is a common heterogeneous condition that can be quite debilitating. There are a number of potential causes of urticaria, and the severity and clinical pattern can vary considerably from patient to patient. Eighty to 90% of patients with chronic urticaria have no specific external cause for their disease, which is therefore labeled "chronic idiopathic urticaria." We now know, however, that up to 30-50% of idiopathic cases may be autoimmune or related to mast cell and basophil abnormalities. There is evidence of an autoantibody to the high-affinity receptor for IgE (FcepsilonRI), specifically binding to the alpha-chain (FcepsilonRIalpha), which may be pathogenic. At this point in time, the gold standard for detecting clinically relevant autoantibodies to FcepislonRI is the functional in-vitro donor basophil histamine release assay. The exact prevalence and role of these autoantibodies is still under investigation. Histamine antagonists are the mainstays of therapy. For patients whose symptoms are not controlled by antihistamines alone, there are a number of adjunct therapy options, but there is still a need to develop better agents for this disease.