(1) Various heterologous tissues incorporated in Freund’s complete adjuvant were given to rats by i.p. injection every two weeks. Kidney emulsions produced a nephrotic syndrome, and a membranous glomerulo-nephropathy. Immunization with kidneys from rabbits, guinea pigs and man produced approximately the same incidence of disease. (2) The renal disease produced by heterologous kidneys appeared immunopathogenetically identical to the lesion elicited by homologous or autologous kidneys. (3) Liver, lung, muscle, intestine and placenta were less effective in producing renal disease than was renal tissues; the disease incidences could not be shown to be significantly different from controls receiving Freund’s adjuvant alone, with the number of animals studied. (4) Kidneys obtained from nephrotic children who had died from intercurrent infections and from patients who had died of lupus with nephritis were just as antigenic in inducing this disease as were healthy human kidneys. Kidneys obtained from children who died in uremia with ‘idiopathic’ chronic nephritis yielded a significantly decreased disease incidence. (5) Kidneys obtained from rats with aminonucleoside nephrosis, experimental autoimmune nephrosis or nephrosis due to heteronephrotoxic sera all yielded decreased incidences of renal disease. This was noted regardless of the duration of the donors’ experimenta