In the present work a polyaniline film was successfully deposited by electropolymerization on single walled carbon nanotube paste electrode. The electrode was characterized using cyclic voltammetry, electrochemical impedance spectroscopy, chronocoulometry and scanning electron microscopy. The modified electrode showed electrocatalytic behaviour towards the anodic oxidation of reserpine. The adsorptive stripping voltammetric behaviour of reserpine at polyaniline film modified single walled carbon nanotube paste electrode (modified-SWCNTPE) was investigated and validated in pharmaceuticals and biological fluids by cyclic voltammetry (CV) and adsorptive stripping differential pulse voltammetry (AdSDPV) in 0.02 M phosphate buffer in the pH range of 2.5-8.5. Cyclic voltammetry has shown that the oxidation process is irreversible over the pH range studied and exhibited an adsorption-controlled behaviour. Further, the overall electrode process is mainly diffusion controlled with adsorption effects. The proposed more sensitive AdSDPV method allow quantitation over the range 0.085 mu g mL(-1) to 0.87 mu g mL(-1) with the detection limit of 0.407 ng mL(-1) and has been successfully used to determine reserpine in bark of Rauwolfia serpentina and in its pharmaceutical formulations. (C) 2013 Elsevier Ltd. All rights reserved.