Abstract: In the studies which are carried out for obtaining more productive, enduring and qualified yield several methods are used. One of these methods is fighting with the agricultural pests using pesticides. Herbicides are a group of pesticides. In the present study, the effects of different concentrations (10-2 M, 10-3 M, 10-4 M and 10-5 M) of Maleic Hydrazide (MH) which is an herbicide, on Helianthus annuus L. chromosomes undergoing mitotic and meiotic cell division were investigated. Preparates which were made for meiotic division and mitotic division were stained according to Feulgen squash procedure. With 10-2 M concentration of MH was not seen mitotic division stage. At the other MH concentrations various meiotic and mitotic division abnormalities were observed. MH concentrations caused a decrease in mitotic index. It is observed that all concentrations of MH caused important abnormalities according to control.