Comet Assay IV interactive video-based software system measures the DNA damage detected using single cell gel electrophoresis (SCGE). Using a high-definition video camera attached to a microscope, the system provides real-time cell scoring by transferring a live video image to a computer screen with no time lag. One of the standard methods for assessing DNA damage, the system uses fluorescent microscopy to examine this damage at the single cell level in a range of applications, including genotoxicity testing, ecotoxicology and clinical diagnostics. “Click and Score” automatic scoring mode allows all measurement parameters to be immediately calculated and recorded with a single click on the comet head. Subjectivity is eliminated from the scoring process as there are no adjustable settings to configure. The system can be incorporated into existing experimental protocols to accommodate current working practices. Auditing and security features make the system fully compliant with OECD Good Laboratory Practice standards.