Effects of two Ni concentrations (50 and 100 µM) on growth, Ni accumulation as well as the activities of glutamine synthetase (GS) and glutamate dehydrogenase (GDH) were studied in shoots of wheat seedlings. Exposure to Ni caused rapid accumulation of this metal in the shoots accompanied by a substantial decrease in the length and fresh weight of these organs. Both aminating (NADH-GDH) and deaminating (NAD-GDH) glutamate dehydrogenase activities were significantly influenced by Ni stress, while GS activity did not change in response to Ni application. The activity of NADH-GDH showed an increase at the end of the experiment and 7 days after Ni treatment it was 68% and 76% higher than in the control, at 50 and 100 µM Ni, respectively. NAD-GDH activity after 1 and 4 days of exposure to a higher concentration of Ni was reduced by 24% and 37%, respectively. However, on the 7th day the activity of this enzyme was enhanced by 150% and 72% over the control level, at 50 and 100 µM Ni, respectively. The obtained results suggest that GDH can play an important role in response of wheat seedlings to Ni toxicity.