For years, bioelectrical impedance analysis has been widely used to evaluate the hydration status in dialysis patients. However, its value in assessment and controlling the hydration status in non-dialysis patients with kidney disease, such as nephrotic syndrome, is little mentioned. Because a simple and accurate method to evaluate the hydration status of nephrotic patients is not available, the aim of the present study was to assess the value of leg electrical resistivity measurement in controlling the hydration status of nephrotic patients. The study investigated 46 nephrotic patients with a mean age of 41.65 +/- 17.15 years, 47.8% of whom were female. The patients were divided into remission and relapse groups according to their serum albumin concentration and oedema. Four hundred and twenty-seven healthy persons were studied as normal control. Their hydration status estimated by leg electrical resistivity was studied. There was significant negative correlation between leg electrical resistivity and percentage of extracellular fluid (ECF) measured by the bromide dilution method. The percentage of ECF estimated by the leg electrical resistivity in the relapse group was significantly larger than that of the remission group, but it was approximately the same in the remission group as in the normal control. For nephrotic patients in the relapse group, after they ahcieved remission, their percentage of ECF estimated by the leg electrical resistivity was significantly less than that before treatment, and was close to that of the normal control. Leg electrical resistivity measurement is a simple, non-invasive and valuable method for controlling the hydration status in patients with nephrotic syndrome.