Abstract: In the lyophilization of solid, liquid or pasty products the product to be lyophilized is placed in an open secondary container of flexible material which is capable of being subsequently closed and lyophilized in a lyophilization apparatus with the container kept open. On completion of lyophilization the container is closed and the closed container withdrawn from the apparatus. Preferably the container is in the form of a bag, e.g. a heat-sealable plastic bag. A lyophilization apparatus is provided with means for supporting secondary containers accommodating product to be lyophilized, means for keeping the secondary containers open during lyophilization and means for closing the containers on completion of lyophilization.