The atypical antipsychotic drug, sertindole, like several other drugs, causes QT interval prolongation. Prolongation of the QT interval on the electrocardiogram has been associated with an increased risk of ventricular arrhythmia, including the more serious form, torsades de pointes, and is thus a safety concern for the authorities. In the case of sertindole, however, the available pharmacoepidemiological studies gathering data from about 10 000 patients documented the lack of increased risk associated to sertindole in comparison to other atypical antipsychotics. On the basis of these data, as well as non-clinical and clinical safety data, the CPMP expert group concluded that, although sertindole has the potential to prolong the QT interval, ¤ ¤ QT interval prolongation does not seem to be a reliable proxy for the risk of severe cardiac arrhythmias”, and there are no clinical data suggesting that sertindole is more arrhythmogenic than are other atypical antipsychotics. To further substantiate this conclusion, two post-marketing surveillance studies have been initiated. One is a randomized comparison of sertindole and risperidone under normal conditions of use. Randomization minimizes selection bias and the intention is that allocation to the two treatment arms will yield comparable treatment groups. While the two drugs will be given in an open-label fashion, all safety data will be blinded and reviewed by an independent safety committee. The other study is an observational study that includes all patients prescribed sertindole who, for whatever reason, will not be included in the randomized study. In all, 10 000 patients are expected to take part in the studies, which will run for at least 1 year.