Bone mineral content (BMC) of the lumbar spine (L2-L4), femoral neck, Ward's triangle and the trochanteric region was measured in 52 consecutive patients on maintenance haemodialysis. In the whole group the median BMC value as percentage of sex- and age-matched normal means was significantly decreased only in Ward's triangle (91.7%; p less than 0.02). In patients with chronic interstitial nephritis there was a significant decrease in bone density in Ward's triangle and the trochanteric region (p less than 0.02). There was no correlation between BMC and time on dialysis or intact parathormone. BMC value did not predict the type of renal osteodystrophy, according to Delling. 17 patients underwent a second investigation after one year. There was a slight fall in mean BMC of the lumbar spine (-0.9%) and Ward's triangle (-1.1%). The fall in mean BMC of the trochanteric region was pronounced (-3.2%). We believe that the observed low demineralisation, which was more pronounced in patients with interstitial nephritis, may be attributable to early and carefully monitored therapy with vitamin D metabolites.