Sperm DNA fragmentation test provides additional information on semen fertility potential that can not be achieved by means of standard motility, morphology and vitality tests. We have selected the Sperm Chromatin Dispersion (SCD) method as simple, fast, accurate, and highly reproducible method for the analysis of sperm DNA fragmentation in semen and processed sperm. The SCD test utilizes the idea that after acid denaturation and removal of nuclear proteins sperm with non-fragmented DNA produce the well seen halo of dispersed DNA loops while spermatozoa with fragmented DNA fail to produce such halo. When somatic cells or spermatozoa with nonfragmented DNA are immersed in an agarose matrix and directly exposed to lysing solutions, the resulting deproteinized nuclei show extended halos of DNA dispersion. The halos correspond to relaxed DNA loops attached to the residual nuclear structure. These deproteinized nuclei are called "nucleoids". The presence of DNA breaks promotes the expansion of the halo of the nucleoid and is the basis for the halo test to detect DNA damage when sperm are treated with an acid solution prior to lysis buffer, the DNA dispersion halos that are observed in sperm nuclei with nonfragmented DNA after the removal of nuclear proteins are either minimally present or not produced at all in sperm nuclei with fragmented DNA.