Abstract: A wood treatment process is disclosed in which in one aspect the wood is impregnated with a waterborne preservative such as CCA at elevated temperature and pressure. The impregnated wood and excess waterborne preservative are separated while the treatment vessel (8) is pressurized, for example by blowing the preservative out of the vessel at the treatment pressure using a pump (10). Kickback may be segregated from the wood once pressure is reduced after the separation of wood and preservative. In another aspect the wood is impregnated with a waterborne preservative and with oil, each of the impregnating steps being performed under pressure and the oil being heated. If the preservative is one such as CCA which is capable of being fixed to the wood the hot oil may enhance this as well as providing water repellency. The oil may be a process oil.