Mice of the BSVS strain were immunized intracutaneously with bovine and intracutaneously and intraperitoneally with homologous adrenal homogenates in complete Freund's adjuvant. Immunization with bovine adrenal elicited the production of antibodies directed against an adrenal-specific antigen restricted to the bovine species as well as non-organ specific antibodies directed against the bovine species. These organ-specific antibodies directed against the bovine species. These organ-specific antibodies were demonstrated by passive haemagglutination, gel precipitation and immunoelectrophoresis. Antisera against bovine adrenal reacted stronger with antigen extracts prepared from the cortico-medullary junction than with extracts of isolated medulla or outer cortex indicating that the adrenal antigen may be located primarily in the cortical zona reticularis. Immunization with mouse adrenal did not elicit production of antibodies reactive with murine or bovine adrenal, or histological lesions in the adrenal gland.