Lumbar spinal stenosis, most commonly caused by hypertrophic changes in the soft tissues of the spinal canal, is itself a clinical entity, but in the early phase it can also serve as a factor influencing general back disorder morbidity. It can be identified reliably by measuring the anteroposterior diameter of the dural sac on myelography films and/or the transverse area of the dural sac on computed tomography (CT) scans. In the present study, 76 patients with general back disorders were examined with ultrasound (US) transabdominally through the intervertebral disc. In those 50 patients (66%) in which all three of the lowest lumbar intervertebral spaces could be visualized, the measurements made by US differed by +/- 5 mm from those obtained by myelography and +/- 25 mm2 from those made by CT. In a subset of ten patients with spinal stenosis, US was able to demonstrate the small size of the dural sac, but the cause of the stenosis could not be reliably evaluated. In addition to diagnosing central spinal stenosis, ultrasonography is also well suited for screening purposes.