Abstract: The purpose of the present work was to evaluate the oxidative stress and the antioxidant defense system in two-lettuce cultivars Lactusa sativa var. longifolia-baladi (baladi cv.) and Lactusa sativa var. crispa-mignonette (mignonette cv.). The plants were subjected to two drought levels and treated with two concentrations of gibberellic acid (GA3). The application of drought stress increased significantly the lipid peroxidation and catalase activity in the two cultivars while it induced significant decreases in protein content, peroxidase and ascorbic acid oxidase activities as compared to control. Treatment with gibberellic acid alleviated the adverse effects of drought. It could be concluded that the lowest concentration of GA3 was more effective on alleviating the adverse effect than the highest concentration. Also it was found that mignonette cultivar was more tolerant to drought than baladi cultivar.