CONTEXT AND OBJECTIVE: An association between chronic idiopathic urticaria (CIU) and autoimmune thyroid disease (ATD) has been reported. However, there have not been any reports on whether ATD raises the risk of angioedema, which is a more severe clinical presentation of CIU. Thus, the aim of the present study was to evaluate whether the risk of angioedema is increased in patients with CIU and ATD. DESIGN AND SETTING: Case-control study including 115 patients with CIU at a tertiary public institution. METHODS:The patients were evaluated with regard to occurrence of angioedema and presence of ATD, hypothyroidism or hyperthyroidism. RESULTS: Angioedema was detected in 70 patients (60.9%).