A gas syringe developed at the University [See figure in the PDF file] of Oregon Medical School has a cartridge-loaded plunger that fits a standard 50 cc. syringe. The unit is sterilizable. It uses cartridges that are inexpensive and readily available, filled with about 4 liters of a wide choice of gases. The instrument makes gas a convenient roentgenographic contrast agent and should, therefore, increase its clinical use.