Leaf beetles (Oulema sp.) are among the most important pests of grain cereals in Europe, they are most likely to attack oats, then barley and wheat. Larvae are fed by biting narrow stripes on leaves leaving epidermis. Because of such way of nutrition and white epidermis, white and narrow stripes are being formed on the leaves. One of the main problems i.e. shortcoming of chemical measures is the phenomenom of weaker susceptibility of the pest to insecticide i.e. the occurrence of resistance. The aim of this research is to determine a different level of sensitivity of adult forms of Cereal leaf beetle to active substances from the group of organophosphorus insecticides, pyrethroids and neonicotinoids. During 2019, adult forms of Cereal leaf beetle are collected from 11 locations in the area of Continetal Croatia. Insect individuals are transported to Department of Agricultural Zoology where laboratory experiments were set up according to the IRAC test method number 007. Treatment of populations with active substance chlorpyrifos resulted in resistance on locations Kobilić and ĐurĎevac and there is a possibility that the resistance on organophosphorus insecticides is present on other, until now unexplored locations. Research has shown low efficiency of cypermethrin on almost every location, and compared to the previous research it can be said that resistance of Cereal leaf beetle to pyrethroids is present. All surveyed populations of Cereal leaf beetle showed resistance to active substance thiacloprid. By transmitting agrotehnical measures and good agricultural practice, it is possible to delay or prevent the occurrence of resistance, and when applying insecticides it is necessary to pay attention to the change of preparations with different mechanism of action from the previously used.