Abdominal computed tomography (CT) was performed on nine patients with primary aldosteronism in an attempt to evaluate the utility of this noninvasive procedure in localizing aldosterone-producing adenomas. Confirmation of the diagnosis of primary aldosteronism was made by demonstrating elevated urinary aldosterone excretion, low PRA, and failure of plasma aldosterone to fall after acute saline load. Each patient had diagnostic lateralizing adrenal venous sampling and adrenal venography before unilateral adrenalectomy. The CT scan correctly predicted unilateral adenoma in the four patients whose tumors measured the largest in diameter at surgery. Bilateral tumors measuring 0.8 and 1.2 cm on scan (at or below the resolution capabilities of our scanner) were falsely predicted in two patients. The CT scan failed to identify an adrenal abnormality in three patients whose tumors measured 0.9, 1.0, and 1.0 cm in greatest diameter. It is concluded that at its current state of precision, the CT scan is of diagnostic utility in primary aldosteronism when a large adenoma is present. In our patients, the adrenal venogram and CT scan were equally accurate. The sampling of adrenal venous blood for aldosterone and cortisol remains the gold standard for localization of unilateral adenoma.