Significant positive effects could be achieved in a placebo-controlled double-blind study through the administration of 800 mg of garlic powder over a period of four weeks. Spontaneous thrombocyte aggregation disappeared, the microcirculation of the skin increased by 47.6% (from 0.63 +/- 0.13 to 0.93 +/- 0.22 mm/s), plasma viscosity decreased by 3.2% (from 1.25 +/- 0.34 to 1.21 +/- 0.43 mPas), diastolic blood pressure by 9.5% (from 74 +/- 9 to 67 +/- 5 mmHg), and blood glucose concentration by 11.6% (from 89.4 +/- 8.8 to 79.0 +/- 11.9 mg/dl). The vascular protection of garlic as atherosclerosis prevention by influencing the mentioned risk parameters for cardiovascular diseases must be pointed out. Especially interesting is the thrombocyte aggregation inhibiting effect. Thus, the application of garlic may be useful in case of acetylsalicyclic acid intolerance.