A method of manufacturing a bag (20) for the cryopreservation of thermolabile liquids. The manufacturing method is characterized by being versatile, simple and inexpensive and allows to manufacture single and multi-compartment bags without modifying the main sealing molds (31, 32). The relative size and the number of the compartments (28) can be modified without change in the molds. Only a closure sealing tool (50) must be adjusted as a function of the number of chosen compartments (28). The process is compatible with standard high frequency sealing processes. This method provides bags (20) with uniformly thick walls and with a predetermined bag volume.
