The injection of normal or ínfarcted homologous renal tissue induced hypertension in the rat comparable to that which follows unilateral infarction of the kidney. The serum of such rats exhibited precipitin reactions against trypsinized digests of isologous kidney and arterial tissues. The presence of anti-kidney and anti-artery components in the serum was also indicated by the binding of fluorescein-conjugated globulins to the glomerular and basement membranes and arterial components of normal kidney. Globulin was localized in the small arteries of kidneys exhibiting endarteritis and damage to the elastic membrane. Suppressants of antibody reactions (cortisone and 6-mercaptopurine) inhibited the development of hypertension following infarction of the kidney. The demonstration of the presence of anti-kidney components in the sera of certain patients with hypertension and those with renal disease suggests that this phenomena of an autoimmune reaction against renal tissue which has been induced experimentally in the rat may also play a role in human disorders. When this process affects that part of the nephron normally concerned in the maintenance of the normotensive state, hypertension ensues