In the light of European directive (98/8/CE) on efficacy and toxicity of biocides coming into force on 2008, wood preservation research is now focussing on environmentally-friendly wood preservatives. Boron-based preservatives are considered as a good alternative regarding their low mammalian toxicity and their broad spectrum effectiveness against wood degrading organisms like fungi and termites. Nevertheless, their high solubility into water is accelerating their leaching out of wood under outdoor exposition. Combinations of vegetable oil and borates have been tested as wood preservatives. Three vegetable oils varying by the permeability of their dry film are evaluated for boron retention and biological resistance to termites and decay fungi. It appears that vegetable oils provide boron retention of about 30% of initial amount depending on oil drying properties. Linseed oil is the most efficient, followed by soybean oil and rapeseed oil. Durability of C.japonica sapwood specimens has been enhanced by application of linseed oil alone but not enough to reduce termite's attack of Coptotermes formosanus. Treating wood with a 1.0% w/w boric acid solution prior to oil treatment protects C. japonica from termite and fungi degradations. Efficiency against termites is mainly due to boron retention but hydrophobic oil also forms a barrier decreasing fungi penetration.