Embryonic stem cells (ESCs) are culture-adapted pluripotent cells derived from the inner cell mass of the blastocyst-stage embryo. ESCs provide unique opportunities to study the molecular basis of the process of differentiation that gives rise to all the somatic cell types of the body, including cells of the cardiac lineages. Many protocols have been established to obtain cells of the cardiac lineage from ESCs in vitro. More recently, a clearer picture of the regulatory networks governing cardiac differentiation has begun to emerge. Herein, we summarize the current methods to obtain cells of the cardiac lineages from ESCs and present a review of the signaling pathways, transcription factors, and target genes involved in cardiac differentiation. © 2009 by Begell House, Inc.