A d etailed description is given of an apparatus and procedure designed to m easure t he piezoresistive effect in semiconductors over an extended temperature range. A tensile forc e up to 1 kilogram can be appli ed to the sample by means of a calibrated beam balance. The apparatus has b een used for m easurements on indium antimonide over the range 78 0 K to 300 0 K , and tensile s tresses of the order of 5 X 107 dynes p er square centimeter can be applied t o samples that ar e cut in a sp ecial manner.