INTRODUCTION THIS REVIEW of autoimmune thyroid disease will highlight the recent advances made in understanding the control of the autoimmune process particularly at pathogenetic and therapeutic levels. Many novel techniques have recently been applied to the investigation of thyroid autoimmunity although the results obtained have not always clarified the overall picture. These new methodologies are discussed and attention is also focused upon experimental thyroiditis produced in a variety of animals. We believe that these models have been neglected somewhat by clinically oriented investigators. Yet their use originally led to the foundation of autoimmune concepts, and experimental thyroiditis continues to provide major insights into the possible etiology and pathogenesis of the human counterpart. Before discussing thyroid disease in detail however, it is worth considering the current themes in autoimmunity in general.