The electrooxidative behavior and determination of metformin hydrochloride, anti-hyperglycemic drug, on a pyrogallol modified carbon paste electrode were investigated using cyclic voltammetry and differential pulse voltammetry. Metformin hydrochloride shows an irreversible oxidation behavior over a wide interval of pH (Britton-Robinson buffers, pH 2-9). The peak current varied linearly in the range comprised between 8.0 × 10 -7 and 6.0 × 10 -6 mol/L with detection limit of 6.63 × 10 -8 mol/L and limit of quantification of 2.21 × 10 -7 mol/L. The method was proposed for the determination of metformin hydrochloride in dosage forms and urine.