Isoniazid is a tuberculostatic agent effective active compound. A glassy carbon electrode (GCE) was modified with an electropolymerized film of p-aminobenzene sulfonic acid (p-ABSA) in phosphate buffer solution (PBS). The electrochemical properties of isoniazid on modified electrode were studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The polymer film-modified electrode was used to electrochemically detect isoniazid. The polymer film had excellent electrocatalytic activity for the oxidation of isoniazid. A linear calibration curve for DPV analysis was constructed in the isoniazid concentration range 2x10(-5) - 1x10(-4) mol L-1. Limit of detection (LOD) and limit of quantification (LOQ) were obtained as 3.05x10(-6) and 1.01x10(-5) mol L-1 respectively. Isoniazid was determined in tablet dosage form. The proposed method exhibits good recovery and reproducibility. The mechanisms of electropolymerization were also suggested.