summary A prolonged qtc-interval may cause potentially life-threatening arrhythmias. Almost all drugs used in psychiatric practice are able to prolong the qtc-interval. There are some indications that clinicians are not sufficiently aware of the risks of qtc-interval prolongation in clinical practice. By drawing up a list of risk factors associated with prolonged qtc-interval and by correcting for these factors as far as possible, one should be able to reduce the overall risk of potentially lethal arrhythmias and administer more appropriate pharmacological treatment.