A new potentiometric membrane sensor responsive to uric acid has been developed. The membrane sensor is based on aliquat-urate, as an ion pair, and 2-NPOE as a plasticizer. The sensor exhibits fast, stable, and Nernstian response for the hydrogen urate over the concentration range 10−2–10−5M and pH 5–7. Many substances and ions cause no interference. A standard addition method has been used for determination of uric acid in serum, urine, and commercial standard uric acid and the results of determination were 3.0 to 7.2 mg%, 0.21 to 1.04 mg% and 4.5 × 10−5to 4.9 × 10−3mg%, respectively.