Haloxyfop-ethoxyethyl (HE) is a herbicide active against most grasses, whereas dicotyledonous plants are rather resistant to it. The effects of HE on the growth of wheat seedling leaves (cv. Almari) as well as the activity of several enzymes involved in the plant defense system against stress such as superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (POX), ascorbate peroxidase (APX), were studied. The growth of wheat leaves was inhibited by 50% 12 h after the HE treatment. The changes observed in the enzyme activities suggest that the herbicidal effect on enzyme activity depends on the distance between the place where the HE was applied and the section of the leaf analyzed as well as on the duration of the plant with the HE. The changes in SOD, POX, and CAT activities observed in the leaves of the wheat treated with the compound might mean that HE induces oxidative stress in the species studied. These results may confirm the hypothesis related to the mechanism of graminicides action.