This paper reports an electroanalytical method developed for tert-butylhydroquinone (TBHQ) determination in biodiesel in the presence of surfactant Triton X-100 (T-100). T-100 was shown to improve the electroanalytical signal and its use was decisive for direct analysis of TBHQ in biodiesel, only requiring previous dilution of biodiesel samples in methanol. Several parameters were studied and optimized for the development of this methodology. Under optimal conditions, oxidation peak current was proportional to TBHQ concentration in the range of 1.05-10.10 x 10 (6) mol L (1), with limits of detection and quantification of 3.43 x 10 (8) mol L (1) and 1.14 x 10 (7) mol L (1), respectively, by square wave voltammetry (SWV). The results achieved with the proposed method were satisfactory, relative to those obtained using high-performance liquid chromatography (HPLC). (C) 2010 Elsevier Ltd. All rights reserved.