Semen specimens usually are collected by masturbation into a wide-mouthed polypropylene container from a batch or lot tested for lack of sperm toxicity. Mixing a semen sample thoroughly is critical for accurate sperm counts, both initially and throughout each step of semen analysis. Sperm viability testing typically uses a nuclear exclusion stain to determine whether non-motile sperm are alive and not able to move. The component of sperm morphology is one of the most predictive measures of fertility potential and therapeutic outcome. The semen should be examined microscopically for the presence of bacteria, round cells, debris, agglutination, or aggregation. The influence of the female partner in human fertility plays a huge confounding role in both defining fertility and interpreting the association of specific semen analysis measures with fertility. Sperm motility quality controls are available in two formats: frozen aliquots of semen or video recordings on CD-ROM, tape, or digital file.