A drug interaction is caused when one medication affects the action of another medication. Drug interactions can occur through an alteration in drug absorption, distribution, metabolism, and excretion; through an alteration in the pharmacologic action of a medication; or through alteration of a special condition necessary for the action of another medication. Drug interaction detection involves awareness of the problem, adequate medication records, and access to reference materials. The manifestations of drug interactions are often quite varied and can represent anything from a minor to a major clinical problem. Nurses should be aware of the importance of medication record keeping as well as actively involved in seeing that such records are accurately maintained. The management of drug interactions, once detected, is a team effort involving the physician, the nurse, and other health personnel such as the pharmacist. Sophisticated computerized systems for maintaining medication records and for detecting drug interaction problems are already in use in many hospitals and community-based pharmacies. In the future, such systems are likely to be available to the majority of both hospital and community practitioners.