Reported salt tolerant-cultivars (Acala 1517-88, Acala 517-SR2 and salt-sensitive cultivars (Deltapine 50 and Stoneville 825) of cotton were grown for 8 weeks at either 0 or 150 mM NaCl. Analysis of the growth data indicated that the Acala varieties were indeed more salt tolerant than either Deltapine 50 or Stoneville 825. The 150 mM NaCl treatment resulted in more than 40% reduction in growth of Deltapine 50 and Stoneville 825 and less than 30% reduction in the Acala cultivars. Leaf samples from each cultivar were analyzed for the antioxidant enzymes catalase, ascorbate reductase, glutathione reductase, peroxidase, and superoxide dismutase (SOD). At the high salt treatment, no significant difference in SOD or AP activity was observed among cultivars, but the more salt-tolerant cultivars had higher constitutive levels of catalase (121% to 215%). The high salt treatment resulted in a 38% to 72% increase in peroxidase activity and a 55% to 101% increase in GR activity in the Acala cultivars while the activities of these enzymes remained constant or decreased in the more sensitive cultivars. These data indicate that the more salt-tolerant cultivars have a higher capacity for the decomposition of H₂O₂ and a more active ascorbate-glutathione cycle.