Young, unilaterally nephrectomized, female Sprague-Dawley rats were given daily sc injections of 19-nor-deoxycorticosterone acetate (19-nor-DOCA) in oil at a dosage of 100 micrograms/day for 21 days and twice that amount for a further 11 days. One group drank distilled water and another drank 1% NaCl solution. Comparable control groups received oil injections. Another group received DOCA at the same steroid dosage and drank saline. Both 19-nor-DOCA-treated groups rapidly became hypertensive and developed cardiac hypertrophy, as did those given DOCA and saline. Saline consumption was greater in rats receiving 19-nor-DOCA, than in those given DOCA. Rats injected with 19-nor-DOCA and given water to drink showed enhanced growth and developed thymus enlargement and displayed hypokalemia and a reduction in both serum renin activity and corticosterone concentration. Plasma sodium concentration was not affected by any form of treatment. Clearly, 19-nor-DOCA is a potent mineralocorticoid and hypertensogenic agent. Since the parent steroid is known to be present abundantly in the urine of rats with regenerating adrenal glands, although circulating amounts have not yet been ascertained in that circumstance, it may be etiologically involved in adrenal regeneration hypertension, which such rats are prone to develop.