Drought, a natural stress factor has the highest percentage with 26%, when the usable areas on the earth are classified in view of stress factors. Biotic and abiotic stress factors may cause yield loss in plants and affect human and animal nutrition. Amount of lacking yield due to biotic and abiotic stress factors ranged between 65 and 87%. The best option for crop production, yield improvement and yield stability under soil moisture deficient conditions is to develop drought tolerant crop varieties (Siddique et al., 2000). A physiological approach would be the most attractive way to develop new varieties rapidly. Only few studies highlighted the importance of antioxidant enzymes during drought stress. The antioxidant defenses appear to provide crucial protection against oxidative damage in cellular membranes and organelles in plants grown under unfavorable conditions. Thus, plants are equipped with complex and a highly efficient antioxidative defense system which can respond and adapt to drought stress. This system is composed of protective nonenzymatic and enzymatic protection mechanisms. They interrupt the uncontrolled oxidation and serve to maintain the antioxidants in their reduced functional state, that efficiently scavenge ROS (reactive oxygen species) and prevent damaging effects of free radicals. Balance at aerobic metabolism is defined as free radical generation and rapid removal by antioxidant systems. The structure of cells and functional changes of systems, may be damaged by the formation of irreversible oxidative stress. Redox signalling and antioxidative defense systems are very important for protection towards uncontrolled and cascade damage of biotic and abiotic stress factors. In this review, drought, drought types and antioxidative defense system components will be discussed. © 2011 Academic Journals.