1. Radioimmunoassay has been used to detect and estimate the urinary excretion of deoxycorticosterone (DOC) in normal, hypertensive and hypokalaemic subjects. The range of excretions in ten healthy normal subjects was 41–232 pmol (13.7–76.7 ng) daily, with a mean of 124 pmol (41 ng).
2. In fourteen subjects with essential hypertension without metabolic disturbance the range found was 29–144 pmol (9.7–47.7 ng) daily, with a mean of 87 pmol (28.8 ng), which is not significantly different from that in normal subjects.
3. In twelve patients with Cushing's syndrome due to adrenal cortical hyperplasia the range found was 26–542 pmol (8.7–179 ng). Ten of these twelve patients had values within normal limits.
4. Of nine subjects showing hypokalaemia, eight had elevated excretion of deoxycorticosterone with values from 263 to 5515 pmol (87–1820 ng) daily. Seven of these were hypertensive and two were normotensive. The elevated excretion of deoxycorticosterone found in hypokalaemic subjects is thus not confined to those with hypertension.
5. No correlation has been found between excretion rates for aldosterone and deoxycorticosterone. Raised excretion of the latter provides an indicator of disturbed adrenal cortical metabolism.