Oxidative stress generated by aerobic metabolism or from environmental sources is a major cause of damage to organisms. Aluminum is a major toxin in acidic soils and one proposed source of oxidative stress. The enzyme glutaredoxin utilizes a disulfide oxidation-reduction mechanism to detoxify free radicals and is one way organisms have evolved to handle oxidative stress. We have recently isolated a novel glutaredoxin cDNA from soybean; sequence analysis indicates that it is highly similar to other plant glutaredoxin. We grew soybean seedlings in soils containing 0, 20, and 50 mM AlCl3 to examine the effect of high levels of Al on plant growth and on glutaredoxin gene expression. Soybean seedling height and leaf mass varied inversely with the level of aluminum in the soil. Glutaredoxin mRNA levels increased in roots and stems as the level of soil aluminum increased, with the greatest increase seen in the stems. The level of mRNA in the leaves did not change. Glutaredoxin may thus function to detoxify aluminum absorbed into soybean. Enhanced glutaredoxin activity may have a potential role in phytoremediation.