We studied the effects of two garlic sources on systolic blood pressure (SBP) using spontaneously hypertensive rats (SHRs). Beginning at 12 wk of age, male SHRs were fed diets containing either aged garlic extract (AGE) or raw garlic (RG) powder for 10 wk. Both AGE and RG reduced the increase of SBP compared with the control group from 4 wk after beginning the experimental diets. The effect of AGE was accompanied by a decrease of pulse pressure (PP), suggesting an improvement of the pliability of the artery, although RG did not affect PP. However, harmful effects were observed in the RG group, including a decrease in erythrocytes, an increase in reticulocytes, and generation of papilloma in the forestomach. These results suggest that AGE may safely improve several factors related to blood vessel physiology and circulatory disease.