Elderly patients are vulnerable to medication errors and adverse drug events due to increased morbidity, polypharmacy and inappropriate interactions. The objective of this study was to investigate whether systematic medication review and counselling performed by a clinical pharmacist and clinical pharmacologist would reduce length of in-hospital stay in elderly patients admitted to an acute ward of internal medicine. A randomized, controlled study of 100 patients aged 70 years or older was conducted in an acute ward of internal medicine in Denmark. Intervention arm: a clinical pharmacist conducted systematic medication reviews after an experienced medical physician had prescribed the patients' medication. Information was collected from medical charts, interview with the patients and database registrations of drug purchase. Subsequently, medication histories were conferred with a clinical pharmacologist and advisory notes recommending medication changes were completed. Physicians were not obliged to comply with the recommendations. Control arm: medication was reviewed by usual routine in the ward. Primary end-point was length of in-hospital stay. In addition, readmissions, mortality, contact to primary healthcare and quality of life were measured at 3-month follow-up. In the intervention arm, the mean length of in-hospital stay was 239.9 hr (95% CI: 190.2-289.6) and in the control arm: 238.6 hr (95% CI: 137.6-339.6), which was neither a statistical significant nor a clinically relevant difference. Moreover, no differences were observed for any of the secondary end-points. Systematic medication review and medication counselling did not show any effect on in-hospital length of stay in elderly patients when admitted to an acute ward of internal medicine.