Abstract: A process for preparing a fire-resistant cellulosic material which comprises contacting cellulosic material with an aqueous solution of aluminum phosphate wherein the molar ratio of aluminum to phosphorous is less than 1:1, optionally containing a metal oxide, to form an initially treated cellulosic material containing aluminum phosphate and an increased amount of water, removing water from and curing said initially treated cellulosic material to form a fire-resistant cellulosic material. The cellulosic material is preferably wood and the wood is preferably a shingle or plywood.