Abstract Methyl bromide treatment of potatoes reduced their glutathione content in a dose-dependent fashion. Using [ 14C]methyl bromide, it was found that the major portion of the chemically bound residue could be extracted into 60% ethanol. Three compounds, S-methylcysteine, γ-glutamyl- S-methylcysteine, and S-methylglutathione, accounted for most of the radioactivity in this extract. Similar results were obtained for oranges fumigated with [ 14C]methyl bromide. It is proposed that potatoes, oranges, and probably other vegetables and fruits can metabolize methyl bromide by glutathione S-transferase-catalyzed conjugation with glutathione. Hydrolysis of S-methylglutathione by peptidases would yield γ-glutamyl- S-methylcysteine and S-methylcysteine. A similar study of an extract of methyl bromide-treated maize did not provide evidence for the formation of these compounds indicating that glutathione was not involved to any appreciable extent in the lowering of methyl bromide residues in this commodity.