Stem cells have recently gained attention within Cardiology for their therapeutical application as a treatment in acute myocardial infarction and heart failure. Especially for larger infarct areas, direct myocardial application of bonemarrow derived progenitor cells or the subcutaneous treatment with colony-stimulating factors seems to lead to a small, but noticeable improvement of left ventricular performance. Given this current example of wider therapeutic use of stem cells and progenitor cells it seems warranted to take a closer look at the safety profile of this novel approach. Proarrhythmic properties of embryonic stem cells have already been reported several years ago, yet evidence is lacking that these experimental features are of relevance for daily clinical use of adult stem cells. This review will focus on the available data regarding the proarrhythmic potential of stem cell application based on the available experimental and clinical electrophysiologic data.