Embryonic stem cell-derived cardiomyocytes (ESC-CMs) have applications in understanding cardiac disease pathophysiology, pharmacology, and toxicology. Comprehensive characterization of their basic physiological and pharmacological properties is critical in determining the suitability of ESC-CMs as models of cardiac activity. In this study we use video microscopy and quantitative PCR to investigate the responses of mouse ESC-CMs to adrenoceptor, muscarinic, angiotensin II (Ang II), and endothelin-1 (ET-1) receptor activation. Isoprenaline (10nM-10uM) increased beating rate and contraction amplitude in all beating bodies (BBs), whereas carbachol (up to 1I?M) and the I(f) channel blocker ZD-7288 (10uM) decreased contraction frequency. ET-1 (0.01-100nM) reduced contraction amplitude in all BBs and increased contraction frequency in 50 of BBs; these effects were blocked by the ET(A) receptor antagonist BQ123 (250nM). Ang II (0.01nM-1uM) increased both contraction amplitude (all BBs) and frequency (in 50 of BBs), effects blocked, respectively, by losartan (100nM) and PD123,319 (200nM). These results indicate the presence of functional ET(A) and both AT(1) and AT(2) receptors in murine ESC-CMs, but their expression and or activity appears to be evident only in a limited set of BBs.