OBJECTIVES: Medication reconciliation is the process of obtaining and maintaining a complete and accurate list of the current medication therapy of a patient across health care setting. The combination of recorded and reported (assessed through patient counseling) medication use may increase the accuracy of medication reconciliation process. The objective of this study is to prevent drug-related problems and evaluate the effect of pharmacist-conducted medication reconciliation with patient counseling at hospital admission. METHODS: Patients who were admitted to Internal Medicine in local hospital, with age over 65 years, more than two co-morbidities and receiving more than three regular medications were recruited. Patients with cancer, admitted to the ICU, discharged within 48 hours, or unable to communicate were excluded. Then, these patients were interviewed by pharmacists within 48 hours after admission. The unintentional discrepancies were discussed with the physicians and drug therapy would be adjusted accordingly. The primary outcome of this study included the rate of unintentional discrepancies identified by pharmacists before and after patient counseling and the rate of unreconciled medications resolved by pharmacists. RESULTS: Forty-nine patients were recruited in this study and 129 unreconciled medications were found between October 17 and November 18, 2010. The most common type of discrepancies was omissions with rate of 58.7%. On the other hand, the rate of unintentional discrepancies identified by pharmacist which may cause harm increased from 6.6% to 12.4% after patients counseling and 81.3% of drug-related problem was resolved after pharmacist intervention. Additionally, allergy history was established in 16.3% of patients. CONCLUSIONS: Pharmacist-conducted medication reconciliation with patient counseling improved drug therapy and completeness and accuracy of allergy history. However, this study was only undertaken in patients admitted to Internal Medicine during one month. Implementation of medication reconciliation with patient counseling to further patients, such as surgical patients may be considered.