Even with the use of clinical decision support systems (CDSS), clinicians can still make medication prescribing errors. This study compared frequency, type, and severity of prescribing errors between junior doctors (i.e., those in training with less than 10 years’ work experience) and consultants (i.e., not in training with 10 or more years of work experience).  Overall prescribing errors were low, but junior doctors made more errors than consultants. They also made different types of errors, with junior doctors more likely to make drug-drug interaction errors and consultants making duplication therapy errors. There were no differences in severity of errors. Early education and training with computerized provider order entry (CPOE) and CDSS may reduce errors made by doctors in training.