Optimal fixation is essential for subsequent histopathologic examination in animal testes. Various studies have demonstrated that testicular fixation with different fixatives result in the different morphological details. An earlier study found that adult rat testes fixed in mDF had less tissue shrinkage artifact and better morphological details than the testes in BF fixatives [20]. Another study found that mDF fixation provided better morphological details in the fetal rat testes when compared to BF or 10% neutral buffered formalin (NBF) [21]. The current study finds that adult mouse testes fixed using mDF are superior to the testes fixed using 4% PFA. In addition, we also find that false TUNEL-positive cells are observed in mDF-fixed testes, but not in PFA-fixed testes. The above results suggest that mDF alone is suitable for examination of H&E stained sections, but may not be satisfactory for TUNEL staining in rodent testes.