We measured plasma alpha-human atrial natriuretic polypeptide (alpha-hANP) and catecholamine concentrations during anesthesia and surgery for pheochromocytoma in five patients ranging in ages from 19 to 69. Plasma catecholamine concentrations and systemic blood pressure increased extremely during surgical manipulation of the tumor, while plasma alpha-hANP levels did not change even during surgical manipulation or after removal of the tumor as compared with preanesthetic values. Our findings suggest that plasma alpha-hANP levels were unchanged during anesthesia and surgery for human pheochromocytoma.