Pesticides are designed to kill a very wide range of undesirable organisms, but they simultaneously adversely affect non-target organisms in ecosystems. Dimethoate is an organophosphorous insecticide used widely in agriculture that has an anticholinesterase mode of action. The goal of the study was to assess the effects of dimethoate on catalase, reduced glutathione, and lipid peroxidation in the gills and livers of zebrafish,