The present invention provides an injectable pharmaceutical composition containing, as an active ingredient, paclitaxel, an anti-cancer agent. The injectable pharmaceutical composition comprises an effective amount of paclitaxel, which is dissolved in polyoxyethylated castor oil, alcohol, and an injectable aqueous solution. A sufficient amount of CO.sub.2 is added to stabilize paclitaxel in the injectable pharmaceutical composition to make the injectable pharmaceutical composition to a pH about 5.0.