Stem cells, which have a great capacity for self-renewal and can differentiate into at least one committed cell type, exist in embryonic and adult organisms of many phyla. Although stem cells of various types from mice and other lower organisms have been studied for many years, it was not until the derivation of stem cell lines from human embryos in 1998 (1,2) that the idea of stem cell-based therapies became widespread for the treatment of a range of disorders from Alzheimer’s disease to type I diabetes. Efforts to generate insulin-producing islet cells from murine and human embryonic stem (ES) cells followed the establishment of these ES cell lines. In this review we will discuss the derivation procedures and growth characteristics of ES cell lines from these two species and the status of research to promote their differentiation into cells of the endocrine pancreas lineage.