The unlimited proliferative ability and plasticity to generate other cell types ensures that stem cells represent a dynamic system apposite for the identification of new molecular targets and the production and development of novel drugs. These cell lines derived from embryos could be used as a model for the study of basic and applied aspects in medical therapeutics, environmental mutagenesis and disease management. As a consequence, these can be tested for safety or to predict or anticipate potential toxicity in humans. Human ES cell lines may, therefore, prove clinically relevant to the development of safer and more effective drugs for patients presenting with diabetes mellitus.