An increasing number of our patients are on medication of various types. This increase in prescribed medicines also raises the significant issue of potential drug interactions between those drugs used in dental practice and those taken by the patient. This article addresses those interactions and, where appropriate, puts them into perspective and attempts to quantify the risk. Mechanisms of relevant drug interactions are also discussed. Certain categories of drugs are more likely to be involved in interactions and again these are highlighted. Drug interactions relevant to dentistry can for the most part be prevented. A careful drug history should be taken from each patient and updated on a regular basis.