A load cell utilizing magnetostrictive strain gauges which is suitable for measuring loads up to 300 kg in tensile testing of materials under high hydrostatic pressures up to 15000 kg/cm2 is described. Temperature and pressure variations during tensile testing can be completely compensated by the use of a dummy gauge. The calibration of the load cell under pressure is performed by a coil spring which is calibrated at atmospheric pressure. The calibration curves under pressures up to 13400 kg/cm2 and 200 kg agree with the atmospheric calibration curve within 2%.