Callus tissue from a NaCl-tolerant cell line was transferred to aerated culture tubes containing 150 mM NaCl. Following a 2-hour preincubation, the tubes containing 150 mM NaCl were left untreated to serve as controls or amended with NaCl to a final concentration of 250 mM, 250 mM NaNO₃ , 250 mM KCl, or 500 mM sucrose. The callus tissue was harvested at 30 min, 1 hr, 2 hr, 4 hr, and 8 hr intervals and analyzed for superoxide dismutase (SOD), peroxidase, catalase, ascorbate reductase (AP) and glutathione reductase (GR) activity. Treatment with NaCl resulted in significant increases in peroxidase, catalase, AP, and GR activities within 1 hour and SOD activity within 4 hours. NaNO₃ treatment failed to produce a significant peroxidase response, and KCl treatment failed to produce a significant GR response. The sucrose and KCl treatments resulted in significant increases in peroxidase activity; the sucrose and NaNO₃ treatments produced significant increases in GR activity; and the sucrose, NaNO_3, and KCl treatments caused significant increases in SOD activity. However, in each of these cases, the increases occurred significantly later in time than the increases observed with the NaCl treatment. The catalase response to the KCl treatment also occurred much later than the response to NaCl. These data suggests that the total antioxidant enzyme response observed during NaCl stress in cotton callus tissue is somewhat specific to the combined effects of the Na⁺ and Cl^- ions.