The genotoxicity of different concentrations of insecticide, profenophos (O-4-bromo-2-chlorophenyl O-ethyl S-propyl phosphorothioate) was evaluated at various stages of cell cycle (G1, S and G2) by using the seeds of barley (Hordeum vulgare L.). The aim of this work was to investigate the effects of insecticide profenophos at various stages of cell cycle on germination, seedling height and meiotic behavior in M1 and chlorophyll mutations in M2 generation. From the present study, it can be concluded that the stages of cell cycle were sensitive for the treatments of chemicals and it also showed that the S-phase of cell cycle is more sensitive than other phases of cell cycle.