Under biological conditions plants have to cope with the generation of reactive oxygen species (ROS), which often react radically and are therefore responsible for oxidative damage in cells. Normally, the production of ROS is compensated by an elaborate endogenous antioxidant system consisting of two main mechanisms: antioxidant defense with various enzymes or with non-enzymatic components (e.g. ascorbic acid, tocopherol, glutathione and carotenoids), but under unfavorable environmental conditions like drought the production of ROS can increase dramatically. As the availability of water is of great importance for plant growth, one focus of this applied work is on the changes of the antioxidative network induced by drought. Therefore, in our studies climate chamber grown seasoning herbs (Tropaeolum majus L., Borago officinalis L. and Satureja hortensis L.) are exposed to a mild drought stress which assures that the plant defence network is activated, but there is no damage in the plants. Concentrations of various antioxidants (mentioned above) and photosynthetic parameters are measured in plants without stress, after mild drought and after re-watering. As there is an increasing interest in spices and aromatic herbs, because of their strong antioxidant and antimicrobial properties, another focus of this applied work is on the changes of antioxidants in herbs during drying, storage and processing. In general, herbs can improve flavour, avoid deterioration and enrich foods with vitamins, but the latter are sensitive to e.g. water loss, light or heat and can degrade easily (depending on various factors) which is a major problem for food industry. Therefore, in our studies field grown plant material is dried, stored for months in different types of bags, and processed in different ways before examining contents of antioxidants to simulate industrial conditions and study the degradation processes.