Abstract: In a system for liquefying natural gas containing more than about 1.5 percent nitrogen in which the natural gas is cooled by refrigeration and heat exchange with initial flashing of liquid at a pressure to remove substantialy all of the container nitrogen and with additional stages of flashing of liquid with low pressure flash liquid being passed to liquid natural gas storage and flashed vapors used for heat exchange, recompressed, and combined with the incoming feed the energy requirements of the system are improved by stabilizing the amount of nitrogen recycle in the system by stripping nitrogen from the initial vapor flash with overhead from the stripping heat exchanged within the system to recover its refrigeration and then yielded from the system and with the liquid from the stripping, recycled to the liquid from the initial flashing.