Medical scientists, meeting the challenge of socalled "autoimmune" diseases, have created new techniques and achieved new concepts which are altering markedly our outlook in immunology, immunochemistry, and pathology. Burnet, winner of the Nobel prize for medicine, collaborates with Mackay to present an exposition of this field. They discuss a group of diseases "for which an autoimmune etiology has been established either as a primary or an associated factor, or in which there is some likelihood that autoimmune processes are concerned." Analyzed at length are thyroiditis, systemic lupus erythematosis, certain hemolytic conditions, rheumatoid arthritis, glomerulonephritis, and certain liver and nervous system diseases, while numerous other conditions are treated more cursorily. To diagnose an autoimmune state the authors invoke the following criteria: an increase in gamma globulin, demonstrable autoantibodies against some body component, deposition of denatured gamma globulin at certain sites of elections, accumulation of lymphocytes and plasma cells, some degree of