Developing effective drug therapies for arrhythmic diseases is hampered by the fact that the same drug can work well in some individuals but not in others. Human induced pluripotent stem (iPS) cells have been vetted as useful tools for drug screening. However, cardioactive drugs have not been shown to have the same effects on iPS cell-derived human cardiomyocytes as on embryonic stein (ES) cell-derived cardiomyocytes or human cardiomyocytes in a clinical setting. Here we show that current cardioactive drugs affect the beating frequency and contractility of iPS cell-derived cardiomyocytes in much the same way as they do ES cell-derived cardiomyocytes, and the results were compatible with empirical results in the clinic. Thus, human iPS cells could become an attractive tool to investigate the effects of cardioactive drugs at the individual level and to screen for individually tailored drugs against cardiac arrhythmic diseases. (C) 2009 Elsevier Inc. All rights reserved.