Experiments were conducted to find out an effective combination of chemicals for preservation of rubber wood by diffusion process. The preservatives tried included solutions of inorganic chemicals, organic chemicals and their various combinations. The results indicated that the combinations of borax, boric acid and sodium pentachlorophenate (NaPCP), phosphamidon and oxycarboxin, monocrotophos and oxycarboxin were the best against the sap stain fungus Botryodiplodia theobromae. The growth of Fusarium sp, Aspergillus sp, Trichoderma sp, and Penicillium sp, was significantly less in most of the treatments. Insect borers were effectively controlled by borax + boric acid + NaPCP, dimethoate + tridemprph and copper sulphate + borax. Sodium pentachlorophenate proved to be an important adjuvant for the diffusion treatment of rubber wood though a few combinations devoid of NaPCP also showed encouraging results. The chemical combination of dimethoate and oxycarboxin can be considered an organic substitute in view of the toxicity of PCP compounds. Copper sulphate and its combinations with other chemicals gave good protection against insect borers but were effective against fungi only if NaPCP was added.