The study aim was to investigate the antihypertensive effect after oral supplementation of dried radish leaves powder (DRLP). Angiotensin-converting enzyme (ACE) activity was measured by spectrophotometric assay. The systolic blood pressure (SBP) was measured in spontaneously hypertensive (SHR) and normotensive rats (Wistar) by the tail cuff method after a 4-week diet with DRLP at the level of 2.5% or 5%. The supplementation of DRLP decreased SBP of SHR although the 5% supplementation level did not show any more pronounced effect than the 2.5% level did. The decrease in the SBP observed for both 2.5% and 5% DRLP was accompanied by significant increases of the urinary Na and K excretion. The DRLP supplementation showed a potent ACE-inhibitory activity in pulmonary tissue from both hypertensive and normotensive rats. However, the DRLP supplementation did not affect the SBP in normotensive rats. These results indicated that DRLP exerted an antihypertensive effect in SHR due to the decreased ACE activity and increased urinary Na excretion.