Abstract: An improved vial assembly is provided for storing a quantity of material for cryogenic freezing, such as a sample of semen for use in artificial insemination. The vial assembly includes a locking mechanism to prevent the vial from being opened and then reclosed prior to final use. The locking mechanism includes a pair of apertured locking members, one on the vial, and one on the cap of the vial. The locking members are positioned for mutual alignment only when the cap is securely tightened onto the vial. A locking pin is provided for one-way insertion through the apertures of the locking members to prevent the cap from being removed without severing or destroying the locking pin. With this locking mechanism, the integrity of the contents of the vial is substantially ensured until the vial is selected for use and the locking pin is severed in the presence of a patient recipient. A secondary vial is also provided which mounts to the main vial.