The diagnosis of renal osteodystrophy is straightforward when the disease has reached an advanced stage and the pathology is extremely difficult to treat, whereas it is considerably more complex during the early stages. A study was carried out to assess the sensitivity of some biochemical, hormonal and instrumental markers in the early diagnosis of osteitis fibrosa in patients undergoing hemodialysis due to chronic renal insufficiency. Of these markers, the assay of whole molecule PTH appeared to be the most sensitive and specific biological marker.