A stable aqueous composition including doxycycline in water, a magnesium compound and a nonionic surface active agent, the doxycycline concentration being 20-40 mg/ml of the composition, the molar ratio of magnesium compound to doxycycline being 1:1 - 8:1, the concentration of the nonionic surface active agent being less than 20 percent w/v but not less than 7.5 percent w/v, the composition having a final pH of 5.0 to 7.0. The composition is suitable for pharmaceutical use and is especially useful for either oral, topical or parenteral administration.
