A double-blind, placebo-controlled, randomized, multi-center study was performed with 77 diabetes type II patients to investigate anti-diabetic effects of the French maritime pine bark extract, Pynogenol. Supplementation with 100 mg Pycnogenol for 12 weeks, during which a standard anti-diabetic treatment was continued, significantly lowered plasma glucose levels as compared to placebo. HbA1(c) was also lowered; however, the difference as compared to placebo was statistically significant only for the first month. In the Pycnogenol-group endothelin-1 was significantly decreased, while 6-ketoprostaglandin F(1a) in plasma was elevated compared to placebo. Nitric oxide levels in plasma increased during treatment in both groups, but, differences did not reach statistical significance. Pycnogenol was well-tolerated with ECG, electrolytes, creatinine and blood urea nitrogen remaining unchanged in both groups. Mild and transient unwanted effects were reported for both groups without significant differences. Supplementation of Pycnogenol to conventional diabetes treatment lowers glucose levels and improves endothelial function.