Abstract: OBJECTIVE To investigate drug–drug interactions (DDIs) in the elderly patients in the internal medicine ward, and to provide the basis for clinical medication. METHODS A retrospective study was conducted through looking up the electronic medical records. All patientsaged≥65 years admitted the internal medicine ward of the hospital between June 2015 and October 2014 were included. Drug use situation in the elderly patients during ward stay were investigated and determined whether there was a DDI based on the drug instructions. The drug adverse events caused by DDIs were statistically analyzed. RESULTS A total of 163 patients were ultimately enrolled in the study. The median number of prescribed drugs was 7. The median number of potential DDIs per patient was 3. Potential DDIs were identified in 94 patients, accounted for 57.7%. Actual DDIs were detected in 10 (6.1%) patients. An adverse drug reaction (ADR) resulting from DDIs was detected in 8 patients. In 2 patients, DDIs resulted in diminished therapeutic effect. CONCLUSION In order to ensure the elderly patient safety in medication, physicians should pay attention to DDIs, and try to minimize the number of prescribed drugs and avoid choosing medications that cause adverse DDI to reduce the incidence of DDI-related adverse drug events.