We have designed a method for the assessment of trabecular bone mass (TBM) in a central portion of L4 by means of CT scanning. A total of 29 normal individuals of different ages from both sexes, and 19 hemodialysis patients were studied. 3 selected patients were also studied 1 year later. A good in vivo reproducibility was demonstrated in a dog after repositioning. A positive inverse correlation was observed in the control group between age and TBM supporting the reliability of this method. As reported by others in the postmortem bone mineral analysis of L4, a majority of patients (78.9%) showed a normal or high TBM. From a total of 5 patients with increased TBM only 2 showed radiological osteosclerosis, and 4 of them presented advanced subperiostal resorption suggesting a pathogenetic role of excessive circulating PTH in the genesis of osteosclerosis. A total of 4 had decreased TBM and only 2 of them showed radiological demineralization. 2 patients with decreased TBM, 1 of them under anticonvulsant therapy, experienced a considerable increase in the TBM after 1 year of 25OHD3 therapy. We conclude that this method can be an important help in the early detection and management of renal osteodystrophy.