The effect of adding surface active agents to electrolytes containing nortriptyline hydrochloride on the voltammetric response of a hanging mercury drop electrode (HMDE) was studied. The current signal due to the reduction process was a function of the amount of nortriptyline hydrochloride, pH of the medium, type of the surfactant, and accumulation time at the electrode surface. Addition of Tween-20 to the nortriptyline hydrochloride containing electrolyte enhances the reduction current signal. Voltammograms of the drug with Tween-20 in Britton Robinson buffers of pH 2-11 exhibit a single well-defined reduction peak, which may be due to the reduction of -C=C group. The reduction process was irreversible over the entire pH range, and the mechanism of reduction was postulated oil the basis of controlled potential electrolysis and coulometry. Application of Tween-20 in the electrochemical determination of nortriptylitic hydrochloride using square-wave voltammetry at the HMDE enhanced the detection limit of the analyte concentration from 8.24 ng/ml in the absence of surfactant to 0.92 ng/mL when present.