The first organ system to be established in early embryogenesis is the cardiovascular system which develops upon interaction with hypoblastic cells of the primitive endoderm. Here we focus on recent work on embryoid bodies derived from pluripotent embryonic stem (ES) cells. Ca 2+ oscillations and Ca 2+ signalling pathways during the differentiation of primitive endodermal cell layers are reported. Furthermore, the development-dependent expression of ion channels and the buildup of signalling cascades involved in the modulation of voltage-dependent L-type Ca 2+ channels during early cardiomyogenesis and the formation of functional vascular structures in the process of vasculogenesis and angiogenesis are reviewed. We also report on the use of green fluorescent protein reporter gene expression under the control of cardiac-specific promoters, eg the human cardiac α-actin promoter, which enables the identification and in vivo characterization of cardiomyocytes at very early stages of cardiomyogenesis.