A cryostat with a load capacity of 10 000 lb has been designed for use with standard tensile testing equipment in the temperature range 4 to 300°K. Specimens up to 12.7 cm long can be mounted easily on the grip rods through an opening in the front of the test chamber. The cryostat is used in conjunction with a 10 000 lb Instron tension testing machine containing a stress‐strain recorder and strain pacer.