QT interval prolongation is one of the most important causes of withdrawal of drugs from the market, due to its association with Torsades de Pointes (TdP), a potentially fatal arrhythmia. Although many antimicrobial drugs are capable of inducing this type of arrhythmia, the importance of this effect is usually underestimated. Macrolides, quinolones, azoles, pentamidine, protease inhibitors, antimalarial drugs and cotrimoxazole are the anti-infective agents more frequently associated with this adverse effect. Despite the fact that the risk of QT prolongation and TdP under single antimicrobial therapy is low, these drugs are so extensively used that sporadic cases of this arrhythmia are reported. Moreover, antimicrobial drugs are susceptible to pharmacokinetic and pharmacodynamic interactions with other drugs, which may increase the risk of this arrhythmia. Therefore, physicians must be familiar with not only the antimicrobial drugs capable of producing QT interval prolongation, but also their potential interactions. In addition, patient's specific risk factors of prolonging QT interval or producing TdP must be taken into account. This article reviews the role of anti-infective drugs in QT prolongation, focusing on QT prolongation mechanisms, potential drug interactions, and patients' predisposing factors to this arrhythmia.