Forty cases of primary aldosteronism after adrenalectomy were observed from 1975 to 1993 at Yokohama City University hospital. All of them had adrenocortical adenoma producing aldosterone. These cases are evaluated retrospectively on localization, surgical approach and long term follow up blood pressure. These patients were from 26 to 65 years old (average 46.6), and consisted of 11 males and 29 females. Fourteen adenomas were located on the right adrenal gland, 25 on left, and one case had adenomas on bilateral adrenal glands. On localization study, 39 cases had been correctly diagnosed by combined diagnostic method of selective adrenal venous sampling, selective adrenal venography, adrenal scintigraphy, X-ray CT, and MRI, with each diagnostic values being 65.8%, 69.0%, 72.5%, 96.9%, 100% respectively. This analysis suggests that, in almost cases, it is enough to diagnose the laterality by adrenal scintigraphy, X-ray CT and MRI. Selective venous catheterization is not always necessary to know the laterality of the tumor. For surgical approach to the adrenal gland, 16 adenomas were removed through anterior subcostal incision (transabdominal approach) from 1975 to 1988, and 24 cases through lumbar oblique incision or dorsal incision (extra peritoneal approach) from 1986 to 1993. This analysis reveals that lumbar oblique and dorsal incision provided us superior surgical approach to the adrenal gland. Thirty-eight cases had been followed after adrenalectomy for more than one year (average 57.6 months). Blood pressure had been normalized in 28 cases, but 10 cases had remained hypertensive.(ABSTRACT TRUNCATED AT 250 WORDS)