Medication errors are common in pediatric inpatients, but the best method of addressing them remains unclear. Studies of technological interventions, such as computerized provider order entry, have yielded inconsistent results. In this controlled trial, clinical pharmacists were deployed in the intensive care unit (ICU) and general medical and surgical wards in a pediatric hospital, and their effect on prevention of medication errors was assessed. Serious medication errors (including near misses) were significantly reduced in the ICU. No effect was seen on medication error rates for general ward patients, although the baseline rate of errors was much lower in those areas. A prior review documented the effectiveness of pharmacists at preventing medication errors in a variety of inpatient settings.