Previous studies have demonstrated that milk fermented by specific Lactococcus lactis strains significantly inhibits the activity of angiotensin I-converting enzyme (ACE). However, the relationship between the ACE inhibitor and its in vivo action has revealed discrepancies. Therefore, the aim of the present study was to investigate the antihypertensive and heart rate (HR)-lowering effect of milk fermented by specific L. lactis in a murine model. Spontaneously hypertensive male rats (271 (SD14) g) were randomised into four treatment groups that were orally administered with milk fermented by L. lactis NRRL B-50 571 or L. lactis NRRL B-50 572 at 35 or 50 mg protein/kg body weight (BW), respectively. Further, two more groups were fed with different solutions as controls: a saline solution as the negative control and Captopril (40 mg/kg BW), a proven ACE inhibitor, as the positive control. Blood pressure and HR were monitored by the tail-cuff method before the treatments and at 2, 4, 6 and 24 h post-oral administration. The results demonstrated that milk fermented by L. lactis NRRL B-50 571 as well as by L. lactis NRRL B-50 572 presented an important systolic and diastolic blood pressure- and HR-lowering effect. Thus, milk fermented by specific L. lactis strains may present potential benefits in the prevention and treatment of CVD associated with hypertension in humans.