40 out of 98 patients on chronic haemodialysis show an obviously lowered bone mineral content of the radius (mean -20.4%), 51 patients attain values in the normal range (mean -1%) and 7 subjects slightly increased values (mean +10.9%). A bone mineral loss of 2.5% could be found after long-term observations of this parameter between 6 to 30 months (mean observation period: 15 months). In general a progressive loss of the bone mineral content may be noticed with an increased duration of haemodialysis. This tendency is more distinct after the 40th year of life because of the simultaneous age-depending physiological decrease of bone mass. Abruptly occurring mineral losses of the skeleton may be due to a high incretion of parathyroid hormone and possibly require subtotal parathyroidectomy.