Abstract: An improved cryogenic liquid storage tank features a main tank containing a ullage tank. The top portion of the main tank communicates with the bottom portion of the ullage tank through a pipe segment and an opening in the ullage tank. The pipe segment is dimensioned and positioned so that the main tank fills with incoming cryogenic liquid while the ullage tank remains primarily empty. The restricted flow into the ullage tank causes the flow of cryogen into the main tank to decrease when the main tank is nearly full. This decrease in flow is utilized to terminate the filling of the tank. Removal of product from the main tank decreases the pressure and the liquid level therein so that liquid flows out of the ullage tank and is unable to return.