The present invention provides stable bendamustine-containing pharmaceutical compositions suitable for long term storage. The compositions include bendamustine, a pharmaceutically acceptable salt, and/or a hydrate form thereof, a solvent mixture of N,N-dimethylacetamide and glycerin, and an antioxidant. The bendamustine-containing compositions have less than about 2% of total impurities after two month storage at 25° C./60% RH. The pharmaceutical compositions may be used for treating neoplastic diseases.
