Abstract: The invention provides a continuous process for the preparation of a peracid which comprises reacting hydrogen peroxide with a carboxylic acid in an aqueous medium containing a mineral acid, and extracting the peracid thus formed into an organic phase comprising an organic solvent so as to produce an aqueous solution comprising sulphuric acid and water and an organic solution comprising peracid and organic solvent, wherein the hydrogen peroxide is added to the reaction mixture in a plurality of stages, thereby to limit the concentration of hydrogen peroxide at any location. Preferably the reaction and extraction are effected simultaneously.