Abstract Adverse drug events and medication errors have received extensive study recently in a variety of clinical populations, though compared to many other areas relatively little work has focused on this area in psychiatry, especially with respect to the contribution of error to harm. The goal of this paper is to discuss methodological issues around measurement of medication safety in psychiatric patients. Against the background of a systems approach, a modern perspective of error management is discussed, and a multidimensional procedure for detection and classification of incidents related to the medication process is presented. This method has proven successful in non-psychiatric settings yielding the current best estimate of error rates and providing insight into the underlying causes. While this general approach can be adapted to the psychiatric setting, a number of issues make measurement especially challenging in psychiatry. These include the fluctuating course of psychiatric disorders, reduced patient adherence to the medication process, adverse effects which are often similar to symptoms of the underlying disorder, the frequent use of wide dose intervals depending on the clinical situation, and the presence of many drug-drug interactions. Data collected by means of the presented approach provide a basis for the development of effective strategies to reduce the risk of medication errors and thus improve patient safety in psychiatric care.