The invention relates to a liquid pharmaceutical solution, comprising a solvent, pemetrexed or a pharmaceutically acceptable salt thereof, and an antioxidant. According to the invention, in order to develop such a solution in a manner such that the solution is toxicologically harmless, has a comparatively high stability and can be stored for a comparatively long period of time without becoming turbid or even forming a precipitate, the antioxidant is selected from the group consisting of acetyl cysteine and sodium 2-mercaptoethanesulfonate.
