Abstract: This invention relates to a stable composition and method of making a thickened fluid composition comprising chlorine dioxide. The stable composition includes a mixture containing a chlorite, an acid source, and a thickener component. At least one of the chlorite, the acid source and the thickener component is in particulate form. In an embodiment, the mixture may be a unitary solid body wherein chlorine dioxide is generated upon interaction with an aqueous medium, such as water. A free halogen source may also be added to the mixture in some cases.