The voltammetric behavior of L-dopa was studied at poly sulfacetamide modified glassy carbon electrode (SFA-modified GCE), based on electrochemical oxidation of sulfacetamide. The modified electrode exhibited good selectivity and strong electrocatalytic activity for electrochemical oxidation of L-dopa in Britton – Robinson buffer solution (pH 2). Under the chosen conditions, the oxidation peak currents showed a linear dependence on the L-dopa concentration in the range of 1×10-7 to 1.1×10-6M with limit of detection of 0.3×10-9 M. This method was applied to the determination of L-dopa in human serum and urine with satisfactory results. In addition, L-dopa was determined in presence of ascorbic acid (AA), uric acid (UA) and glucose.