In ICSI, sperm is selected based on its motility and shape under 200–400× magnification. However, sperm morphology, especially the existence of vacuoles, may relate to sperm nuclear DNA fragmentation. Bartoov et al. reported the application of sperm selection under high (1,000–6,000×) magnification, which they referred to as IMSI (intracytoplasmic morphologically-selected sperm injection). In our initial trials, the fertilization, blastocyst development, pregnancy and miscarriage rates of 115 single blastocyst transfer cycles with IMSI or ICSI were 84.0% vs. 75.5%, 47.5% vs. 43.7%, 50.0% vs. 47.4% and 10.0% vs. 11.0%, respectively. Further studies are required to establish the systems and clarify the indications for IMSI.