Whatever promising future clinical application it holds, stem cell research especially embryonic stem cell research is associated with ethical, social and legal controversies. What is so unethical about embryonic stem cell research? The major conflicting unethical issue identified with this research is extraction of embryonic stem cells by embryo destruction. The very embryo which has the capacity to become a human being is destroyed at the onset of its potentiality of becoming one of us. The current view about any clinical research is to look it from the view point of cardinal research principles of autonomy, justice, nonmalfeasance and human dignity. Any research which stands to violate these principles is bound to suffer from moral and ethical controversies. A research that involves embryo destruction will find it difficult to accommodate itself within these cardinal principles.