The goal of a rapid, precise and objective sperm measure of sperm DNA fragmentation, in situ, was realised a quarter century ago by the pioneer development of the sperm chromatin structure assay (SCSA). Since then, measurements on many thousands of sperm samples from a variety of animals and humans exposed to reproductive toxicants and having different diseases or infertility pathologies have solidly established the utility of sperm DNA fragmentation in experimental and clinical settings. New methods have been developed that measure sperm DNA fragmentation by different means such as the enzymatic labelling of broken DNA strands (Tunel assay by light microscopy or flow cytometry) and the light microscope observations of DNA fragments in the Comet assay and the negative loops of sperm chromatin in the Halo sperm assay. These assays have proven useful in the areas of livestock and captive wildlife reproduction efficiency, toxicology and more recently in the human infertility clinic. A significant problem is the lack of quality control and standards of threshold values between laboratories. At this time, only the SCSA has been deemed sufficiently rigorous in methodology and established clinical thresholds for utility in the human infertility clinic.