A sensitive HPLC method with electrochemical detection was developed for the determination of the polyfructosan sinistrin in human plasma and urine. Proteins and interfering components such as glucose were removed from plasma and urine samples by solid phase extraction on C18 cartridges. Chromatographic separations were achieved at 85 degrees C on a 300 mm x 7.8 mm i.d. column, using ion moderated partition chromatography with distilled water at a flow rate of 0.6 ml min-1. After post-column addition of NaOH 0.3 M (0.6 ml min-1), the electrochemical detection of the eluate was performed with a sequence of three potentials (0.05 V, -0.8 V, 0.6 V) of specific pulse duration 300, 100 and 100 ms respectively. Xylose was used as internal standard for the quantitative determinations. The calibration curves were linear (r2 > 0.992) over the working range 5-300 micrograms ml-1. This method has been characterized, validated and applied successfully in a study comparing two modes of glomerular filtration rate determination in healthy volunteers (bolus vs. constant rate infusion of sinistrin).