A 60 year old woman affected by Hashimoto's thyroiditis presented with a history of recurring episodes of urticaria and angio-oedema. Clinical and laboratory evaluation of the patient excluded allergy to external agents, hereditary angio-oedema, and occult infections. A pathogenic relation between Hashimoto's thyroiditis and chronic urticaria/angio-oedema was suspected. However, treatment with L-thyroxine had no influence on the frequency and severity of the cutaneous and mucosal manifestations, which occurred almost daily and required repeated administration of steroids. The patient therefore underwent total thyroidectomy. Cytometric analysis of intrathyroidal lymphocyte subsets showed unusual abnormalities. Urticaria and angio-oedema completely remitted after surgery; 18 months postoperatively the patient was still asymptomatic.