Human Somatic Cell Nuclear Transfer (hSCNT) is a required procedure before derivation of autologous embryonic stem cells (ESC) for clinical treatment. The debate between ethical concerns and the potential for clinical application is still ongoing. Currently, the milestone of deriving hSCNT blastocysts has been achieved. The developmental mechanism for SCNT is similar to the developmental mechanism for fertilized embryos without sperm fertilization. The hSCNT procedure consists of enucleating an oocyte and replacing with a donor somatic cell nucleus; this procedure is more difficult than a parthenogenetic procedure. The difficulties of SCNT involve the cell cycle synchronization between the donor nucleus and arrested ooplasm, suboptimal activation of reconstructed "zygotes", suboptimal culture condition, and incomplete genetic remodeling/epigenetic modification. There are protocols intended to overcome the difficulties, but no center has derived hSCNT ESC yet.