The quality of selected spermatozoa is crucial for the success of assisted reproduction. However, selecting the “best sperm” from an ejaculate or surgically retrieved sample remains challenging. In this chapter, we have reviewed conventional, advanced, and emerging sperm selection techniques, including the most up-to-date reliable evidence-based resources, with emphasis on sperm selection methods and clinical outcomes. Current selection techniques are manual and prone to subjective judgment or experience and effort of laboratory personnel. Despite the large number of publications, the available evidences are not sufficient to support any specific sperm selection technique. The only unanimous agreement thus far is that well-designed, large-scale, sufficiently powered randomized controlled studies are required to evaluate sperm selection techniques; these may include personalized sperm selection, machine learning, and robotics strategies aimed at improving outcomes of assisted reproduction.

Failure to conceive following 12 months of unprotected intercourse is defined as infertility. Both male and female factors can lead to infertility. Various forms of assisted reproductive techniques with different success rates are available to manage both male and female infertility. In some clearly defined cases gestational surrogacy provides the only hope for a couple to have their own genetic children.

According to a number of high-quality studies, intrauterine insemination (IUI) with homologous semen should be the first choice of treatment in the case of moderate male factor subfertility. IVF and ICSI are clearly over-used in this selected group of infertile couples. The limited value of IUI in infertility treatment, as mentioned in the 2013 NICE guidelines, was surely a premature statement and should be adapted to the actual literature. Oxidative stress and high sperm DNA damage is associated with lower pregnancy rates after IUI. Concerning clinical outcome, there is no clear evidence of any sperm preparation technique to be superior. More evidence-based data are becoming available on different variables influencing the success rates after IUI. It can be expected that these findings may lead to a better understanding and use of IUI in the near future.