The voltammetric behaviour of pentoxifylline (1-(5'-oxohexyl)-3,7-dimethylxanthine, PTX) was studied in several supporting electrolytes (Britton-Robinson buffer of pH 2-12, 0.1 M NH3/NH4Cl buffer (pH 9.08), 0.1 M Na2B4O7 (pH 9.30), 0.1 M KCl (pH 6.22). At 0.1 M Britton-Robinson buffer (pH 7.46) PTX gives two peaks at -0.150V and -1.524V, respectively. At low pH values (pH < 5.50), the second peak was obscured by the hydrogen evolution while the first peak is well defined at 0.1M KNO3 supporting electrolyte (pH 6.22). The potential of the second peak is practically pH-independent in the pH range of 6.50-11.00. The peaks (at -0.150V and -1.524V) are attributed to the reduction of Hg(I)-PTX complex and carbonyl group at 5'-oxohexyl moiety of the molecule, respectively. The relationship between peak current of carbonyl group and concentration of PTX is linear in 1.48 x 10(-5) - 1.34 x 10(-4) M concentration range in 0.1 M KCl (pH 6.22). It was observed that PTX has adsorption/desorption characteristics. A plausible mechanism is proposed for the electrode reaction of PTX on the mercury electrode.