In clinical practice, anaesthetists encounter many patients who are on concurrent medication which may have the potential to interact with drugs used during anaesthesia. Many patients are receiving as many as a dozen drugs of various kinds, thus, increasing the risk of a drug interaction occurring. Unfortunately, anaesthetists tend not to report drug interactions which occur during anaesthesia—especially those of a minor nature such as flushing—and hence, the true number of drug interactions is unknown. We have developed a chart indicating the nature of important interactions that the anaesthetist may encounter.