Disinfecting composition comprises an organic peroxyacid selected from phthalimidopercarboxylic acids (I) and a non-ionic surfactant. Disinfecting composition comprises an organic peroxyacid selected from phthalimidopercarboxylic acids of formula (I) and a non-ionic surfactant of formula (II). [Image] z : 1-5; R 1linear or branched 7-20C alkyl or 7-20C alkenyl; and m+n : 0.5-7 (preferably 1-5, especially 1-3). ACTIVITY : Antimicrobial. MECHANISM OF ACTION : None given.