Human alcohol dehydrogenase 3/glutathione-dependent formaldehyde dehydrogenase was shown to rapidly and irreversibly catalyse the reductive breakdown of S-nitroso-glutathione. The steady-state kinetics of S-nitrosogluta-thione reduction was studied for the wild-type and two mutated forms of human alcohol dehydrogenase 3, muta-tions that have previously been shown to affect the oxidative efficiency for the substrate S-hydroxymethylglutathione.