In 60 patients with chronic renal insufficiency and 36 dialysis patients an iliac crest biopsy was performed, on the undecalcified bone morphometric determinations were carried out as well as the aluminium deposition was investigated histochemically. Histologically were found in 3 patients normal findings, in 11 patients a fibroosteoclasia, in 23 patients an osteoidosis and in 59 patients a combination fibroosteoclasia and osteoidosis. 3 oft the 60 patients with a chronic renal insufficiency had aluminium depositions in the polyblasts. Of the 36 dialysis patients 19 (55.4%) had a positive aluminium histology: 30.7% of the patients with osteoidosis and 23.7% with a mixed form. There was a positive correlation to the bone and osteoid volume, to the osteoid surface and a negative relation to the activity of osteoblasts, the absorption surface and the activity of osteoclasts. Aluminium depositions on the mineralisation border might be of importance for the changes.