Out of 446 pupils aged 13-17 years, 115 were found to have a history of back pain. These pupils tended to have decreased lower limb joint mobility and increased trunk length compared with pupils without back pain. In 77 pupils whose site of back pain was identified, 38 had pain associated with the lumbar spine. These pupils had an increased trunk length while those with thoracolumbar or thoracic pain did not. Back pain was more common in those who avoided sports.