Administration of a potent rabbit anti-rat kidney serum to intact as well as bilaterally-nephrectomized rats failed to produce ultrastructural alteration in lungs or adrenal cortices despite localization of the heterologous γ-globulin in these tissues. Quantitative measurements disclosed the 7S globulin fractions of NTS and NRS to be slightly greater in lungs of nephrectomized rats than intact members after their injection, although no apparent difference in such localization was evident by immunofluorescence. Complement was observed only in kidneys following injection of NTS. The results fail to substantiate the occurrence of extrarenal lesions in this system and to indicate that their absence is not necessarily dependent upon quantity of localized anti-basement membrane antibody. They also suggest the importance of fixed complement in this regard.