1. The effect of food collagen, cattle bone collagen-derived (CBC) peptides, on ovariectomy induced increases in blood pressure was examined in stroke-prone spontaneously hypertensive rats (SHRSP). 2. Long-term administration of CBC peptides to ovariectomized SHRSP suppressed the hypertension compared with ovariectomized SHRSP fed standard chow. 3. The CBC peptides showed an inhibitory activity (IC50 = 40 microg/mL) for angiotensin I-converting enzyme (ACE) in vitro. Furthermore, pre-incubation of CBC peptides with gastrointestinal proteases did not change this inhibitory activity of CBC for ACE. 4. These results indicate that CBC peptides may prevent increases in blood pressure in ovariectomized SHRSP by a possible mechanism of an inhibitory action against ACE.