A placebo-controlled, double-blind, parallel group study was performed with 58 patients to investigate effects of French maritime pine bark extract, Pycnogenol, on patients with hypertension. Supplementation of the patients with 100 mg Pycnogenol over a period of 12 weeks helped to reduce the dose of the calcium antagonist nifedipine in a statistically significant manner. The intake of Pycnogenol decreased endothelin-1 concentrations significantly compared to placebo while concentrations of 6-keto prostaglandin F1a in plasma were significantly higher compared to placebo. Values for nitric oxide (NO) in plasma increased in both groups, but the differences were not significant. Angiotensin II concentrations in plasma were lowered in the placebo group to a larger extent than in the Pycnogenol group. Heart rate, electrolytes and blood urea nitrogen were not changed during treatment in both groups of patients. Unwanted effects observed in both groups were of mild and transient nature, such as gastrointestinal problems, vertigo, headache and nausea. Differences in rate of side effects were not statistically significant between the two groups. Study results support a supplementation with Pycnogenol for mildly hypertensive patients.