We established a xenograft line of human adrenocortical carcinoma (ADR-1), and analyzed the hyperaldosteronism induced by the xenograft in vivo. Adrenocortical carcinoma specimens from a 25-year-old woman were subcutaneously inoculated into nude mice (BALB/c-nu/nu) followed by serial passages in vivo. ADR-1 retained the histopathological features (trabecular and sinusoid nests) seen in the primary carcinoma. The patient showed hyperaldosteronism (serum aldosterone >4000 pg/ml) and hypokalemia (serum K 2.1 mEq/l), but did not show hypertension. The nude rat (F344-rnu/rnu) bearing ADR-1 showed hyperaldosteronism (serum aldosterone 3320±1420 pg/ml; control 191±130 pg/ml) and hypokalemia (serum K 3.4±0.4 mEq/l; control 5.2±1.0 mEq/l) in vivo, and hypertension was not obvious. ADR-1 was shown immunohistochemically to retain production of human-specific corticosteroid synthetase. The xenograft ADR-1 will be useful to elucidate the regulatory mechanism of normotensive hyperaldosteronism.