Primary aldosteronism is the commonest cause of potentially curable hypertension when diagnosed in both florid and less florid forms. Genetic screening, so far available only for glucocorticoid-suppressible hyperaldosteronism, permits diagnosis from birth, before any biochemical or clinical abnormalities appear. Biochemical screening using the aldosterone-to-renin ratio permits diagnosis in the absence of raised aldosterone or of hypokalemia. Primary aldosteronism occurs in several familial forms. As well as the variety described in 1966 which is ACTH-dependent and glucocorticoid-suppressible, and not so far associated with tumors, another variety described in 1991 is not glucocorticoid-suppressible and is frequently associated with aldosterone-producing adenomas (APAs). Primary aldosteronism due to adrenocortical hyperplasia, adenoma, or carcinoma can also occur as part of the multiple endocrine neoplasia syndromes, where normoplasia, hyperplasia, benign neoplasia, and malignant neoplasia can exist in the same patient in the same endocrine gland(s) at the same time. The morphology of adrenocortical hyperplasia causing primary aldosteronism ranges from glomerulosa-like (idiopathic hyperplasia of the adrenals) to fasciculata-like (glucocorticoid-suppressible hyperaldosteronism). The morphology of adrenocortical neoplasia causing primary aldosteronism can also be either predominantly glomerulosa-like or fasciculata-like, in our experience equally often. Varying morphology of APAs is associated with varying responses of aldosterone to angiotensin II. Tumors predominantly fasciculata-like are unresponsive to angiotensin II, whereas those predominantly glomerulosa-like are responsive to angiotensin II. Both subtypes can be seen in a single family. Primary aldosteronism represents a spectrum of genetic disorders resulting in hyperplasia or neoplasia, but all are associated with some degree of autonomy of aldosterone production, independent of the renin-angiotensin system.