The disclosure provides a cell freezing and storage bag assembly and a method for using the assembly in banking eukaryotic cells for later seed train expansion. The bag (1) is constructed principally of fluorinated ethylene propylene (FEP) fabric. The bag design includes at least an inlet conduit (2) and an outlet or inoculation conduit (3), which can be sterilely welded to the source of the cells, allowing for "closed system" filling of the bags, which significantly reduces the risk of contamination. The bag also includes a sleeve (8), which can be thermosealed ("S") to form an enclosure, which protects the inlet and outlet conduits against contamination and mechanical damage during freezing, storage and subsequent thawing. In the method, once each bag is filled, its corresponding inlet conduit is sealed ("AS"), and both the inlet and outlet conduits are enclosed within the sleeve. This closed system method obviates the need for sterile environments.
