Abstract From a sample of 958 individuals, a group with no anamnestic recall of notable low back trouble ( n=510) was selected to provide reference values for lumbar sagittal mobility. The measurement technique employed a flexicurve to give angular measures for maximal sagittal mobility in upper (T 12-L 4) and lower (L 4-S 2) regions. The results are presented in the form of reference ranges and modal values, stratified by age and sex. A wide variation in the 'normal' range of mobility at all ages is confirmed. Males had higher values for flexion, whilst females showed higher values for extension and for mobility in the lower region. Sagittal mobility declined with age at different rates in males and females for both flexion/extension and upper/lower measures. Generally speaking, mobility was reduced by some 50% in old age compared with childhood, the reduction being most marked for measures of flexion and upper lumbar mobility.