Despite the various sources of stem cells (adult, embryonic, fetal, derived from umbilical blood), scientists argue that embryonic stem cells (ESC) provide the most stable and promising results in treatment of different diseases and in regenerative medicine due to their special abilities. Taking into consideration that the only source of ESC is a human embryo, research on such cells are the most controversial ethically and morally, this influences different countries to adopt different policies governing the research on ESC, source of embryo, legality of their use. The essential role in addressing this controversy is the Bioethics Committees of National and International level. This article is aims to highlight this problem and the position of various countries on this issue.