Treatment of read canary grass leaves with phenol, 4-chlorophenol, naphthalic anhydride and phenylethylisothiocyanate increased glutathione S-transferase activity by 1.4-2.4-fold (control 17 U g(-1) DW). Benzothiadiazole, beta-aminobutyric acid and salicylic acid increased activity by 1.3-1.8-fold. Total glutathione pool was increased by the toxic compounds by 1.2-2-fold and by the elicitors 1.4-1.6-fold (control 593 nmol g(-1) DW). Unlike the other compounds, benzothiadiazole and salicylic acid did not decrease the redox state. Benzothiadiazole acted synergistically with chlorophenol on glutathione S-transferase and glutathione levels and counteracted the decrease in redox state caused by the xenobiotic. Reed canary grass thus has a strong potential to neutralize toxic compounds, which may be further enhanced by elicitors.