A pencil-lead electrode modified with a thin film of bismuth, that is "environmental friendlier" than mercury, was used for electrocatalytic reduction of 2-nitrophenol (2-NP) and 4-nitrophenol (4-NP) by differential pulse voltammetry and net analyte signal standard addition method (NASSAM). The modified electrode has electrocatalytic behavior toward reduction of 2-NP and 4-NP. Because of similar structures of analytes, at the modified electrode they have high overlapped signals that determination of them in the presence of each other is impossible with univariate methods. NASSAM is a very recently introduced method that is a new modification of the standard addition method, which was used for the simultaneous determination of 2-NP and 4-NP.