UNLABELLED:We previously reported on an objective new tool that uses quantitative electroencephalography (QEEG) normative- and referenced-electroencephalography sampling databases (currently called Psychiatric EEG Evaluation Registry [PEER]), which may assist physicians in determining medication selection for optimal efficacy to overcome trial-and-error prescribing. The PEER test compares drug-free QEEG features for individual patients to a database of patients with similar EEG patterns and known outcomes after pharmacological interventions. Based on specific EEG data elements and historical outcomes, the PEER Report may also serve as a marker of future severe adverse events (eg, agitation, hostility, aggressiveness, suicidality, homicidality, mania, hypomania) with specific medications. We used a retrospective chart review to investigate the clinical utility of such a registry in a naturalistic environment. RESULTS:This chart review demonstrated significant improvement on the global assessment scales Clinical Global Impression - Improvement and Quality of Life Enjoyment and Satisfaction - Short Form as well as time to maximum medical improvement and decreased suicidality occurrences. The review also showed that 54.5% of previous medications causing a severe adverse event would have been raised as a caution had the PEER Report been available at the time the drug was prescribed. Finally, due to the significant amount of off-label prescribing of psychotropic medications, additional, objective, evidence-based data aided the prescriber toward better choices. CONCLUSION:The PEER Report may be useful, particularly in treatment-resistant patients, in helping to guide medication selection. Based on the preliminary data obtained from this chart review, additional studies are warranted to establish the safety and efficacy of adding PEER data when making medication decisions.