Abstract: Some patients with non-obstructive azoospermia can get their offspring with paternal genetic material by the micro-injection with haploid spermatid or spermatid nucleus into oocytes（round spermatid injection，ROSI or round spermatid nucleus injection，ROSNI）. The haploid spermatid can be obtained from semen or by testicular biopsy. Although some ART babies fertilized successfully by ROSI were reported，there are still many unresolved problems, such as low rate of fertilization and low rate of baby birth, at present. One of the main causes of fertilization failure, or low fertility rate, is that the haploid spermatid can′t be accurately identified. The advantages and disadvantages of different methods to identify round spermatids, as well as mechanisms, were reviewed, so as to help ART laboratory to improve ROSI outcomes.

Key words: Azoospermia, Spermatids, Spermatogonia, Sperm injections, intracytoplasmic