Dexamethasone suppression adrenal scintigraphy is routinely used in the clinical assessment of patients with aldosteronism. To determine the relation between adrenal iodocholesterol uptake and aldosterone secretory activity, iodocholesterol uptake in dexamethasone-suppressed dogs was measured during salt loading and salt depletion. Sodium loading resulted in decreases in both serum aldosterone and adrenal iodocholesterol uptake. Sodium depletion was associated with increases in both serum aldosterone and iodocholesterol uptake. From these studies we calculate that under basal conditions, approximately 10% of adrenal iodocholesterol uptake is angiotension dependent, and approximately 50% is ACTH dependent. The administration of dexamethasone results in an increase in the sensitivity of adrenal scintiscanning in the assessment of adrenal zona glomerulosa function.