A new method for the quantification of the nitric oxide (<dot>NO) scavenging activity of compounds in aqueous solutions is described using an amperometric <dot>NO sensor. After correction for the spontaneous degradation of <dot>NO, second-order rate kinetics of the scavenging reaction are observed. The rate constant for haemoglobin found with this method is comparable with that found with an established spectrophotometric method. To demonstrate the capability of the method, several sulfur-containing compounds were tested (GSH, GSSG, S-methyl glutathione, N-acetyl cysteine, lipoic acid and dihydrolipoic acid). Of these compounds, only those that contained a thiol group displayed a considerable <dot>NO scavenging activity.