Laser flash photolysis experiments shows that the rate constant for the reaction of the glutathione thiyl radical with nitrogen monoxide to give S-nitrosoglutathione is lower than 2.8 +/- 0.6 x 10(7) M-1 s(-1). The conversion of the thiyl radical to its carbon-centred form at 10(3)s(-1) exceeds the formation of S-nitrosoglutathione when physiological concentrations of nitrogen monoxide are taken into account. (c) 2007 Elsevier Inc. All rights reserved.