Abstract: The invention provides bleaching and detergent compositions containing a diacyl peroxide of general formula ROOR.sup.1 in which R represents a phthaloyl radical and R.sup.1 a radical such that ROOR.sup.1, ROOR and R.sup.1 OOR.sup.1 are all soluble in mildly alkaline aqueous solutions. The compositions, optionally containing a persalt such as sodium perborate, preferably in a mole ratio of one mole per mole of diacyl peroxide, are particularly suitable for washing or bleaching at a temperature of from 30.degree.- 60.degree. C. The invention also provides diacyl peroxide compositions desensitized to impact or abrasion by intimate contact with a diluent, e.g. magnesium sulphate, lauric acid or sodium tripolyphosphate and protected against destructive interaction with other components of the bleaching on detergent composition during storage. Preferred diacyl peroxides include diphthaloyl peroxide, especially for colored fabrics.