Pycnogenol, a standardized extract of Pinus pinaster bark, was tested for its antimicrobial activity against 23 different pathogenic prokaryotic (gram-positive and gram-negative) and eukaryotic (yeast and fungi) microorganisms. Pycnogenol inhibited the growth of all the tested microorganisms in minimum concentrations ranging from 20 to 250 microg/mL. Thus, Pycnogenol in concentrations as low as 0.025% could counteract the growth of all the strains investigated in our study. These results conform with clinical oral health care studies describing the prevention of plaque formation and the clearance of candidiasis by Pycnogenol.