The ApopTag® Peroxidase In Situ Oligo Ligation Kit specifically detects apoptosis by staining only cells that contain double-stranded breaks that are blunt-ended or have a one base 3' overhang (cells containing nicked, gapped, 3'-recessed, 3'-overhanging ends longer than one base and single-stranded ends are not detected). The high analytic specificity of the ApopTag® ISOL Kit minimizes background due to non-specific labeling of DNA. The specificity can be exploited to more readily identify apoptosis in systems presenting cells with both apoptosis and DNA damage or apoptosis and necrosis. Results are visualized using brightfield microscopy.