Human embryonic stem cells (hESCs), initially thought to be immune privileged cells, are now known to be susceptible to immune recognition. Human induced pluripotent stem cells (iPSCs) have been proposed as a potential source of autologous stem cells for therapy, but even these autologous stem cells may be targets of immune rejection. With clinical trials on the horizon, it is imperative that the immunogenicity of hESCs and iPSCs be definitively understood.