The authors describe 10 patients with associated diffuse toxic goiter and thrombocytopenic purpura and a female patient with associated goiter and a three-shoot autoimmune peripheral cytopenia. In 8 patients thyrotoxicosis preceded the appearance of thrombocytopenia, in 3 patients, both the conditions were diagnosed at a time. In 4 patients, the measurements were taken of the IgG content on the surface of platelets according to Dixon et al. In 3 patients, the IgG content turned out to be appreciably elevated, in one patient, the content of IgG was within normal, however the latter patient was examined after prednisolone intake that had given rise to an increase in the platelet count. Two patients who received radioactive iodine and three patients treated by thyrostatic drugs were later on subjected to splenectomy. In 4 patients, thrombocytopenic purpura remitted after subtotal strumectomy. One female patient was subjected to sectoral resection of the thyroid. Two years after surgery the patient, who was in an euthyroid state, developed thrombocytopenia which required splenectomy. It is possible that in the latter case there was no direct relation between the two diseases. The relationship between the two autoimmune diseases, diffuse toxic goiter and thrombocytopenic purpura, remained unclear in other 10 cases. The relationship between the diseases under consideration and approaches to specifying the character of such a relationship are under discussion.