A technique is described for surgical removal and in vitroarterial perfusion of the dog adrenal gland. The left adrenal was perfused at 38C under a hydrostatic pressure of 55 mg Hg for 50, 120, or 180 min with Krebs Ringer bicarbonate buffer containing glucose. Perfused adrenals neither gained weight nor was there visible evidence of adrenal swelling. Secretion of 17-hydroxycorticosteroids (17-OHCS) continued at a basal level of 0.2–1.3 ¼g/min throughout control perfusions. Pulse addition of ACTH at 30 and 70 min into affluent perfusate increased 17-OHCS secretion between 1.4–14.1 ¼g/min and 1.4–11.4 ¼g/min. respectively. These secretory levels approximated those levels reported for blood perfused dog adrenals in vivo. The results suggested that the dog adrenal secreted high quantities of corticoids in vitro without the presence of an extra-adrenal source of steroid precursors. (Endocrinology94: 822, 1974)