Abstract: Fire retardant cellulosic material comprises from 0.4 to 2.0% by weight of tin and from 0.4 to 8.0% by weight of boron based on the weight of the cellulosic material. The fire retardant material is prepared in a two-stage or a one-stage process. The two-stage process comprises impregnation of the material with an alkaline solution of an alkali metal stannate or stannite, followed by impregnation with an aqueous solution of boric acid and drying. The one-stage process comprises impregnation of the material with a stable aqueous colloidal suspension of hydrous tin oxide stabilized with an alkali metal salt of boric acid having a pH in the range of from 4 to 8, followed by drying.