This paper describes the electrochemical behavior of the nitrofurazone (NFZ), in predominantly aqueous medium, in the absence and presence of glutathione (reduced form) (GSH), L-Cysteine (Cys) and O-2 using a highly boron doped diamond electrode (HBDDE). In presence of [Thiol] >= 3.7 x 10(-2) mol L-1 NFZ is directly reduced to RNO-Thiol adducts in an electrochemical process involving two electrons and two protons. On the other side, 02 acts as a RNO2 center dot- scavenger and the velocity constant for the reaction, kO(2), is 60 L mol(-1) s(-1). The process is catalytic and can be used to the analytical determination of NFZ in the range of 9.9 x 10(-7) <= [NFZ] <= 1.1 x 10(-5) mol L-1 at pH 8.0, with sensitivity of 2.2 x 10(6) mu A mol(-1) cm(-2) and detection limit of 3.4 x 10(-7) mol L-1. The analytical parameters were similar to those obtained at pH 4.0 using the direct reduction of NFZ to the respective amine derivative in a process involving six electrons and six protons. The characterization of NFZ global reduction process in aqueous medium and at relative low scan rate, 100 mV s(-1), was only possible due the intrinsic superficial characteristics of the HBDDE, which stabilize the RNO2 center dot- free radical, allowing to work in a large potential window, without losing the RNO2 center dot- oxidation signal. (c) 2006 Elsevier Ltd. All rights reserved.