In this study, the genotoxic effects of four synthetic pyrethroids (cypermethrin, cyphenothrin, deltamethrin, and permethrin) alone and their combinations with different rates of piperonyl butoxide (PBO) were studied using the wing somatic mutation and recombination test (SMART) of the Drosophila melanogaster . In the first stage, lethal concentration values (LC ₂₅ or LC ₅₀ ) of the synthetic pyrethroids and concentrations of PBO used for the synthetic pyrethroids were determined. Then, Drosophila larvae were exposed to lethal concentrations of synthetic pyrethroids and combinations with different rates of PBO (1:0.25, 1:0.5, 1:0.75, 1:1, and 1:2). According to the obtained results, alone and with the PBO of the mixtures of the four synthetic pyrethroids are not genotoxic when compared with the negative control. In addition, the PBO when used alone demonstrated negative results when exposed to 1, 5, and 25 ppm concentrations, while demonstrating positive result when exposed to 50 ppm concentration. However, the PBO did not show any co-genotoxic activity with the four tested synthetic pyrethroids. Results of this study will take an important place in human and environmental health with the new results for the PBO ratios in insecticide formulations.