Neonates are highly vulnerable to medication errors because of their extensive exposure to medications in the neonatal intensive care unit (NICU), the general lack of evidence on pharmacotherapeutic interventions in neonates and the lack of neonate-specific formulations. We searched PubMed and EMBASE to identify relevant original studies published in the English language. Eleven studies were identified on the frequency of medication errors in the NICU. The highest rate was 5.5 medication errors per 100 prescriptions; however, medication error rates varied widely between studies, partly due to differences in the definition of an error and the rigor of the method used to identify medication errors. Furthermore, studies were difficult to compare because medication error rates were calculated differently. Most studies did not assess the potential clinical impact of the errors. The majority of studies identified dose errors as the most common type of error. Computerised physician order entry and interventions by clinical pharmacists (e.g. the participation of pharmacists in ward rounds and review of patients' prescriptions prior to dispensing) were the most common interventions suggested to improve medication safety in the NICU. However, only very limited data were available on evaluation of the effects of such interventions in NICUs. More research is needed to determine the frequency and types of medication errors in NICUs and to develop evidence-based interventions to improve medication safety in the NICU setting. Some of these research efforts need to be directed to the establishment of clear definitions of medication errors and agreement on the methods that should be used to measure medication error rates and their potential clinical impact.