A tube picking mechanism is designed for use in an automated, ultra-low temperature (e.g., −80° C.) storage and retrieval systems which stores biological or chemical samples. The samples are contained in storage tubes held in SBS footprint storage racks that are loaded into trays located within an ultra-low temperature freezer compartment (−80° C.). A tube picking mechanism resides in a tube picking chamber that is located adjacent the freezer compartment. The tube picking chamber is maintained at about −20° C. when the tube picking mechanism is in operation. The tube picking mechanism includes a cache within the tube picking chamber to facilitate fast paced shuttling of the tube racks from the freezer compartment into the tube picking chamber. The shuttle has a clamping mechanism to secure a tube rack in place when a gripper head picks a tube from the rack. The system also includes a push pin that pushes on the bottom of the respective tube as it is being picked from the tube rack. A one-dimensional bar code reader is included within the tube picking chamber. The gripper head is able to move vertically and rotate within the field of view of the one-dimensional bar code reader in order to facilitate identification and reading of one-dimensional bar codes located on the sidewall of picked storage tubes. The system also uses fans to facilitate efficient cooling of the tube picking chamber.