Abstract: One hundred and five fingernail specimens were measured by standard alkaline picrate method. Seventy of these were from normal individuals （37 aged, 33 preaged）. Other 35 specimens were obtained from patients with chronic renal failure （10 aged, 25 preaged）. The result showed that Ncr of normal aged and preaged subjects was 7.02±0.21 and 7.24±0.69mg/100g nail respectirely. Terewas no significant difference between the two groups. Ncr of aged and preaged patients with chronic renal failure was 14.35±0.80 and 14.85±0.87mg/100g nail respectirely. It suggest that there is no correlation between the amount of Ncr and age, whereas a positive linearcorrelation is present between Ncr and Scr （Aerum creatinine）. Our results suggest that the method may be of va-lue in estimating the renal failure in the aged people and, possibly, in determining the duration of renal failure.