Abstract: A wood treating composition is provided, comprising an aqueous solution containing (a) a specified amount of a water insoluble zine compound, namely zinc carbonate, zinc oxide or zinc thiocyanate; (b) one of (i) a specified amount of ammonium thiocyanate, or (ii) a specified amount of ammonium carbonate, or (iii) a specified amount of both ammonium thiocyanate and ammonium carbonate; and (c) a specified amount of a zinc compound solubilizing amount of ammonia, the composition having a pH of 9 or more. The components may be provided by dissolving ZnO in an aqueous ammonia solution containing carbonate ions, or by dissolving zinc carbonate in an aqueous ammonia, or by means of an aqueous ammoniacal solution of Zn(CNS).sub.2. The composition may also include one or more of the following: (a) cupric ammonium ions, (b) a vinyl polymer latex, (c) optionally, an acidic organic surfactant compound which is soluble in said ammnoiacal salt solution, or (d) an additional fungicidal agent.