Complexities of testis structure and function are emphasized in morphometrical and genotoxic evaluation by statistical analysis. F-344 rats were treated with azinphos methyl, cyclophosphomide, and dichlorvos. And Brdu was injected with intrapertionially before sacrifice. The existence and degree of DNA damage were measured by Brdu labeling index which represented relative amount of Brdu incorporated in DNA, morphometric change was evaluated by the relative length of tubular diameter in circular seminiferous tubules and the number of spermatogonia per Sertoli cell in stage IX seminiferous tubules.