Motivation: The availability of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) makes them a promising tool for cardiac-safety assessment as proposed by the CiPA committee (1) because the assessment of cardiac action potentials in hiPSC-CMs provides for a cell-based integrated electrophysiological drug response assay. Moreover, patient specific iPSC-CMs have the potential to be used as isogenetic human disease models. We attempted an in-depth electrophysiology characterization of commercially available iPSC-CMs, namely Cor.4U cells provided by Axiogenesis (Cologne, Germany) via automated patch-clamp utilizing the in-house developed CytoPatch™2 automated patch clamp platform to develop new cardiac safety pharmacology assays. Moreover, first attempts have been performed to transfer these methods to patient specific iPSC-CMs. Methods: iPSC-derived cardiomyocytes were approached in the whole-cell configuration using the CytoPatch™ automated patch-clamp equipment (2). We applied a complex assay including several voltage-clamp protocols aiming to discriminate the main transmembrane ion currents: INa (voltage-gated Na+ current), ICaL (L-type Ca2+ current), Ito (transient outward current), delayed rectifier (IK DR) K+ currents IKr and IKs, inward rectifier IK1, and If (funny current), plus stimulus-elicited action potentials (AP) in current-clamp mode. To suppress spontaneous pacing we injected continuously 10 or 20 pA of hyperpolarizing current. APs were subjected to automated analysis with own-written algorithms (3). Statistical significance was assessed using two-tailed Student’s t test for independent samples (p < 0.05). Results: In Cor.4U® cardiomyocytes kept in vitro for 10 to 15 days, different cardiomyocyte types have been distinguished based on AP features: ventricular (APD50/APD90 ³ 0.7), atrial/nodal, and an S-type with narrow spikes and exponential decay. In the ventricular type cells, mean APD90 between 529±328 ms and 1230±981 ms (mean±S.D.) have been observed on the different experimental days. Upstroke velocity was between 54.2±24.6 ms and 64.1±16.1 ms (mean±S.D.). Nifedipine markedly reduced APD90 (49.8% and 40.8% of control values at 1 and 10 mM, respectively) and APD50 (16.1% and 12%), cisapride 0.1 mM increased APD90 to 176% of control, and tetrodotoxin 10 mM decreased the maximum slope of phase 0 to 33% of control and shortened APD90 to 80.4%. In patient specific iPSC-CMs the relevant cardiac inward currents have been found in voltage-clamp whole-cell recordings. In current-clamp recordings the effects of compounds on ventricular cardiac action potentials have been investigated. Conclusion: Automated patch-clamp technology can be successfully applied for characterization and pharmacology assays on human iPSC-derived cardiomyocytes.