The reduction of 4-nitrophenol (4-NP) has been carried out on a modified glassy carbon electrode using cyclic and differential pulse voltammetry (DPV). The sensor was prepared by modifying the electrode with lithium tetracyanoethylenide (LiTCNE) and poly-l-lysine (PLL) film. With this modified electrode 4-NP was reduced at -0.7V versus SCE. The sensor presented better performance in 0.1moll(-1) acetate buffer at pH4.0. The other experimental parameters, such as concentration of LiTCNE and PLL, pulse amplitude and scan rate were optimized. Under optimized operational conditions, a linear response range from 27 up to 23200nmoll(-1) was obtained with a sensitivity of 3.057nAlnmol(-1)cm(-2). The detection limit for 4-NP determination was 7.5nmoll(-1). The proposed sensor presented good repeatability, evaluated in term of relative standard deviation (R.S.D.=4.4%) for n=10 and was applied for 4-NP determination in water samples. The average recovery for these samples was 103.0 (+/- 0.7)%.64935-42