Sunflower (Helianthus annuus L) is a high – value agricultural crop that is suitable for human consumption and livestock nutrition as well. It is cultivated in rotation, and growing is recommended in same area at least every four to six years. Before sowing of sunflower, it is important to take care of the pre-culture and the history of the use of herbicides in the previous crop. Some herbicides used in previous crop (residues), can lead to a variety of adverse consequences. The time period during which a herbicide remains active in the soil depends primarily on the characteristics of the molecule (degradation, water solubility, dosage, etc.) and environmental factors (soil type, temperature, precipitation, etc.). The aim of this graduate thesis was to investigate the sensitivity of sunflower plants to the use of reduced (1/8, 1/4, 1/2), recommended, double and four times higher doses of herbicide mesotrione. Evaluation of the effect of the treatment was determined by a visual evaluation of damage (0 - 100%) and by weighing the fresh and dry overhead mass of sunflower. Research results indicate an increase in damage depending on the increase of the mesotrion dose. The lowest percentage of damage (10%) of the overhead mass was recorded 14 days after application of herbicide treatment wich is applied the lowest dose (1/8 recommended dose) and the highest (73,3%) treatment wich is a four times higher of the recommended dose. During te second evaluation (21 days after application), in all treatments, showed an increase of progression initial damage from 16,6% 1/8 doses of mesotrione to 95% with four times higher than recommended dose. At the last evaluation (28 days after application) at all treatments, damage continued to have a progressive effect, up to almost complete decay of sunflower (96,6%) at four times higher dose. Dry mass (dry weight) sunflower to all herbicidal treatments was considerably less than control. The minimum (10,9%) reduction of dry weight was recorded on treatment with the lowest dose applied while the for times higher dose of mesotrione than recomended casue almost completely (92%) reduction of sunflower plants.