Drug related problems often occur in patients with renal impairment. Incorrect drug dose and inappropriate drug choice according to the patients' renal function were the most common problems. Patients with the most complex drug treatment, i.e. with increasing degree of renal impairment and increasing number of drugs, are at greater risk of drug related problems. The high acceptance rate for the pharmacist's interventions supports the inclusion of a clinical pharmacist in the multidisciplinary treatment team to increase awareness and optimisation of the drug treatment in this patient group.