A novel nighttime reaction sequence involving 1) nitrate radicals, 2) sulfate radicals and ultimately 3) hydrogen peroxide is proposed. According to a grossly simplified model calculation this sequence may lead to a twofold increase in the background hydrogen peroxide level during one night. This increase may be accumulated over a long period. Presumably an increased level of hydrogen peroxide will mean increased ozone depletion in the lower stratosphere. Proper modelling and more experimental work is needed to assess the importance of this proposed source of hydrogen peroxide. ¿ American Geophysical Union 1995