Determination of trace amounts of uric acid (UA) in serum is of great importance since its level in serum may show disorders in purine metabolism. With this method, trace amounts of UA in blood serum can be determined by a fast and simple procedure using differential pulse polarography (DPP). The limit of detection was estimated to be 2 x 10(-7) M (S/N = 3), lower than that given in previous studies. Among the many electrolytes studied, the best electrolyte condition was found to be 0.05 M phosphate buffer, pH 10-12, in 0.1 M KNO3. The peak for UA appeared at about -0.15 V in this medium, which responded well to standard additions and high reproducibility was obtained. The validity of the proposed method was tested in serum samples by spiking known concentrations of UA to serum samples and high recovery was obtained. The interference effect of dopamine (DA) and ascorbic acid (AA) was eliminated simply by the addition of Fe(III), in a very fast and quantitative reaction. The proposed method was successfully applied to the determination of UA in serum using only very small quantities (0.5 mL) of serum. There is no need for long and tedious extraction or separation procedures, or to prepare modified electrodes in order to eliminate the interference by AA and DA.