Sera of 50 patients suffering from Addison's disease were studied for antibodies to human adrenal antigens by complement fixation, tanned cell hemagglutination, precipitation, and indirect immunofluorescence techniques. Positive results in one or more tests were obtained with 22 sera. Adrenal antibodies of exquisite organ specificity were found. However, a few of the positive sera cross-reacted with extracts of human testis and thyroid. Nuclear antibodies were encountered in nine addisonian sera; their occurrence was unrelated to adrenal antibodies.