Abstract: The present invention relates to a novel pharmaceutical composition for the preparation of effervescent powders or tablets incorporating ibuprofen or one of its pharmaceutically acceptable salts as the active ingredient. This composition comprises an effective amount of ibuprofen or one of its pharmaceutically acceptable salts; a pharmaceutically acceptable effervescent system comprising at least one alkali metal carbonate and at least one organic acid, preferably in a sufficient amount to give a pH below about 8; and at least one pharmaceutically acceptable antioxidant in a sufficient amount to stabilize the ibuprofen. This composition has a remarkable stability both in powder form and in tablet form.