Plants are exposed to wide range of different stresses. As plants have only limited mechanism for stress avoidance, they require flexible means for adaption to changing environmental conditions. This study was carried out to reasearch the changes of antioxidant enzymes activities as caused by water stress in four lettuceUactuca sativa) lines. Four lettuce lines exposed to water stress showed premature senescence as evidenced by the consistenent reduction in the content of total soluble protein and total lipid. Water stress also caused decreased activities of superoxide dismutase, catalase, ascorbate peroxidase, but decrease rates were different. Catalase activity was decreased much more than that of ascorbate peroxidase that suggest catalase reacted with hydrogenyperoxide directly not with ascorbate peroxidase.