This investigation was performed to study biomechanical properties of human intervertebral discs as a function of age. 178 specimens from 21 spinal sections (Th9-S1, 5-84 yr) were subjected to axial dynamic compression; the load being 950 +/- 540 N. The results revealed three distinct age ranges: From the first to the middle of the third decade: axial deformability decreases within the thoracic region, and remains almost constant within the lumbar spine; creep decreases in both parts. From the middle of the third to the beginning of the sixth decade: the biomechanical behavior scarcely alters. Afterwards: axial deformability remains unchanged; creep, however, again increases within the lumbar spine. The results reveal the discs behave most efficiently within the age range where the incidence of back pain is maximal.