This invention relates to the regulation of vascular endothelium biocompatibility and to the inhibition of vessel wall cell and other types of cell hyperplasia following vessel wall dysfunction and/or injury. More particularly, the invention relates to the dietetic and pharmaceutical preparations of 13-hydroxyoctadeca-9Z, 11E-dienoic acid (13-HODE) and its use in reducing or inhibiting vessel wall hyperlasia and restoring vessel wall biocompatibility.