Bone status was assessed in 15 children and adolescents with predialysis chronic renal failure (CRF) and in 25 subjects with end-stage renal failure (ESRF). The mean age in the whole group was 14.6+/-3.2 years and CRF had been recognized 5.8+/-4.0 years earlier. The mean age, body size, duration of the disease and Tanner stages did not differ significantly between patients with predialysis CRF and ESRF. The control group consisted of 890 healthy subjects matched with patients for age. Bone mineral density (BMD) was measured by DPX-L (Lunar, Madison, WI) at the spine (s-BMD) and total body (TB-BMD); quantitative ultrasound (QUS) was performed by DBM 1200 (IGEA, Italy) at the hand phalanges (Ad-SoS). Laboratory investigations included the evaluation of intact parathyroid hormone (i-PTH), total and ionized serum calcium, and serum phosphate. In the whole group of patients the following mean values were obtained: Ad-SoS 1952+/-79 m/s (significantly lower than in controls, who had Ad-SoS 2022+/-85 m/s, p<0.05; the difference remained significant after adjusting for body mass index), s-BMD 0.87+/-0.22 g/cm2 ( Z-score -1.6), TB-BMD 0.92+/-0.12 g/cm2 ( Z-score -1.44), i-PTH 276+/-300 pg/ml, total calcium 2.46+/-0.19 mmol/l, ionized calcium 1.14+/-0.08 mmol/l, phosphate 1.68+/-0.61 mmol/l. Skeletal measurements correlated significantly with age, body size and Tanner stages (also after adjusting for age), while significant correlations of these parameters with the duration of CRF and laboratory investigations (except of correlations of i-PTH with Ad-SoS and with TB-BMD in predialysis patients) were not observed. None of the studied variables differed significantly between predialysis and dialysis patients. In conclusion, both predialysis and dialysis children and adolescents showed a decrease in BMD and quantitative ultrasound measurements. The severity of skeletal alterations was similar in the early phase (predialysis patients) and end stage (dialysis patients) of the disease and did not show a tendency to progress with CRF duration.