A case of chronic urticaria associated with thyroiditis is described. The diagnosis of autoimmune thyroid disease (Hashimoto's disease) rested on the presence of nodular goiter, thyroid dysfunction and significantly elevated thyroid microsomal antibodies (greater than 6,400). Skin biopsy showed changes suggestive of leucocytoclastic vasculitis. Immunological studies showed few abnormalities (low titers of antinuclear antibodies and rheumatoid factor) but a search for circulating immune complexes was negative, and serum complement levels were within normal range. The patient complained of severe pruritus and polyarthralgia but no systemic involvement occurred. Urticaria vasculitis has never previously been described in association with thyroid autoimmunity. This suggests the possibility of an autoimmune cause of urticaria. The urticaria improved and disappeared after treatment with levothyroxine. The frequent clinical latency of thyroiditis warrants systematic testing for circulating anti-microsome antibodies in women presenting with an apparently idiopathic chronic urticaria.