The subacute toxic effects of separate and combined use of piperonyl butoxide and resmethrin (cismethrin) on the liver and kidneys of male mice were investigated. It is known that when given alone, pyrethroids are toxic and their toxicity becomes more complicated when they are co-formulated with piperonyl butoxide. In the present study, macroscopic and microscopic changes were determined in the liver and kidney tissues. Furthermore, biochemical alterations and clinical neurotoxic effects were observed. Toxic effects were more evident in the group subjected to combined use. The results obtained demonstrated that, in mice, piperonyl butoxide and resmethrin are directly toxic to the liver and kidneys. The toxic effects and tissue degeneration were more widespread in the group subjected to combined use. Key words: Piperonyl butoxide, resmethrin, sub-acute toxicity, histopathology, liver, kidney.