Primary cultures or established cell lines of vertebrates are commonly used to analyse the cytotoxic potential of chemical factors, drugs and xenobiotics in vitro. An alternative approach will be provided by permanent lines of pluripotent embryonic stem (ES) cells, which are able to differentiate into specialised somatic cell types in vitro. Here, we demonstrate the capacity of ES cells to generate functional cardiac, neuronal and pancreatic cells. We show that during ES cell differentiation, tissue-specific genes, proteins as well as functional properties are expressed in a developmentally regulated manner recapitulating processes of early embryonic development. We present data that show the use of ES-derived cardiomyocytes and dopaminergic neurons in toxicological studies and the potential of ES-derived pancreatic beta-like cells in future in vitro assays. The application of these differentiation systems to human ES cells opens up new perspectives in basic and applied toxicology.