This article reviews the current findings on the topic of gender differences derived from effects of sex steroid hormones on cardiac repolarization and drug-induced torsade de pointes. Published studies have shown that sex-related differences exist in clinical cardiac electrophysiologic measurements, and that gender is an independent risk factor in vulnerability to certain types of arrhythmia. For example, women are especially susceptible to increased arrhythmia risk in response to QT-prolonging drugs. However, a number of questions remain--especially regarding the specific influence of sex steroid hormones in gender differences. Further experimental or clinical investigations are necessary to elucidate gender differences in cardiac repolarization, QT interval prolongation, and susceptibility to cardiac arrhythmias.