In patients with chronic renal insufficiency and dialysis patients as well as in normal persons determinations of vitamin A in the serum and in the bone were performed and related to the parameters of the bone metabolism and to the histomorphometric investigation of the bone. The vitamin A serum levels were significantly increased in the two groups of patients, however, did not show any differences between the patients with an osteoidosis or the combination of osteoidosis and fibroosteoclasia. There were no correlations to calcium, phosphorus, PTH and to the alkaline phosphatase as well as to the individual histomorphometric data. The vitamin A content of the bone was low and did not show any differences to the normal persons. On the other hand, there were significant relations between the parathormone and the parameters of the regeneration and the absorption of the bones. An additional influence of vitamin A on the bone disturbance, eventually by the activation of the osteoclasts cannot be excluded.