In a cross-sectional study of 2684 males from a range of occupations the prevalence rate for back pain was 20% (11% disc disease and 9% undetermined pain) and about half of these had pain related to the lower back with the remainder being located in the dorsoscapular or cervical regions. Follow up study of a cohort of 1249 of these workers over a two year period indicated that the incidence rate of low back pain in that group was about 1% per annum. When sickness absence certificates were studied the annual absence from back pain (all sites) was 1323 days per thousand employees. However, when confirmation was obtained from general practitioners about non-specific rheumatic diagnoses this figure rose to 1707 days. The prevalence of disc disease is higher among those engaged in heavy rather than among those in light work, and also among those required to adopt a chronic stooping posture at the place of work. A device designed to record lumbar EMG, antero-posterior and lateral posture of the lumbar spine and intra-abdominal pressure designed to be used in work places over a complete shift is described and traces obtained under laboratory conditions are presented.