Abstract: The construction and performance characteristics of all-solid-state carbetapentane ion-selective electrode are described. The electrode, based on ion-pair complex with phosphotungstate, showed rapid and Nernstian response to carbetapentane in the 1×10^-2～2×10^-6M concentration range with a cationic slope of 59 mV/logC. The electrode responses were not affected by pH in the range 2.2～7. Direct potentiometry and potentiometric titration in micro-volume were used to determine carbetapentane in pharmaceutical preparations, urine and blood with satisfactory results.