Abstract: A sanitizing composition capable of destroying pathogens present at a locus and/or of removing biofilm present at a locus (for example MRSA or Legionella) aqueous solution: at least one surfactant, preferably non-ionic; at least one antimicrobial agent, preferably a biguanide and/or quaternary ammonium compound; at least one acid, preferably organic; and chlorine dioxide. The sanitizing composition is formed by making two precursor compositions, one containing the chlorine dioxide stabilised in an alkaline medium, and the other containing acid. These precursor compositions are mixed to form a concentrate composition. A dwell time is allowed. Once the dwell time has elapsed the concentrate composition is diluted with water, and the resulting sanitizing composition can be used.