Abstract: A high pressure steam sterilized plastic container holding an infusion solution therein is prepared first by providing a flexible container made of plastic material and holding an infusion solution. The container is then sterilized in a saturated steam atmosphere which is pressurized by a gas inert to the infusion solution and does not contain oxygen. The infusion solution in the container is not deteriorated after the sterilization.

Abstract: A plastic container containing an infusion solution which may not allow deterioration of the infusion solution over a long period of time, is prepared by providing a container which is made of a flexible plastic material having a heat resistance able to withstand heat of autoclaving sterilization and which holds an infusion solution containing components which may easily deteriorate upon contact with oxygen; the container is packaged with a first packaging material which consists of a plastic material having a gas permeability and a heat resistance able to withstand the heat of autoclaving sterilization. The container packaged with the first packaging material is sterilized by autoclaving in an atmosphere of saturated steam containing substantially no oxygen. The packaged and sterilized container is cooled while substantially maintaining a pressure of autoclaving sterilization by introducing an inert gas into the atmosphere.