A 37-year-old woman developed acquired haemolytic anaemia and thrombocytopenic purpura. At the same time there were signs of hypothyroidism. Incomplete heat antibodies (direct Coombs test) were demonstrated as cause of the haemolytic changes, while high-titre thyroglobulin and microsomal thyroid antibodies as cause of the immunothyroiditis explained the hypothyroidism. Although serological demonstration of platelet antibodies did not succeed, the clinical and haematological findings suggested immunothrombocytopenia. Antibodies against smooth muscle produced no clinical symptoms. The activity of the incomplete heat autoantibodies was diminished as result of immunosuppressive treatment and haemolytic signs regressed. Platelet count rose and the haemorrhagic diathesis disappeared. Thyroid antibody titre rose at first but then markedly decreased. There was no demonstrable effect on the hypothyroidism so that it was necessary to administer thyroid hormones. This is the first published case of such immunopathological triad resulting from immunothyroiditis.