The mechanical function generally ascribed to the intervertebral discs is to act as "shock absorbers" between the vertebral bodies so as to prevent them from rubbing together and becoming traumatized. This shock absorbing function of the discs depends upon their capacity to absorb energy. Therefore, it was surprising to find no data, in the literature surveyed, on the energy absorbing capacity of the intervertebral discs although their biomechanical behavior and other physical properties have been studied quite extensively in recent years. This is particularly true for the lumbar discs because of their clinical importance in low back pain and sciatica. The total energy absorbed to failure was determined for twenty-three last thoracic discs, twenty first lumbar discs, twenty-two second lumbar discs, twenty-two third lumbar discs, twenty-three fourth lumbar discs, and thirteen fifth lumbar discs from the bodies of eighteen white males, two white females, and six negro males.