BACKGROUND The measurement of depression severity is an important aspect of both clinical and research practices. However, studies examining the self-report Beck Depression Inventory (BDI) and the clinician Hamilton Depression Rating Scale indicate only moderate correlations. The aim of this study was to examine the correlation between two self-report measures, the revised BDI, the Hopkins Symptom Checklist with the clinician rated, Montgomery-Asberg Depression Rating Scale. The secondary aim was to investigate patient factors which contribute to discordant ratings. METHODS Depression severity and demographic, clinical, personality, cognitive, and personality factors that may contribute to a self-report-clinician rated discrepancy were examined in 177 adult outpatients with a Major Depressive Episode (DSM-IV) participating in a randomised clinical trial comparing CBT and IPT for depression. All assessment was conducted prior to treatment randomisation. RESULTS Self-report and clinician rated depression were moderately correlated. Individuals with higher clinician rated depression severity, increased levels of rumination and females were more likely to have higher self-report rated depression (BDI-II and SCL-90) than clinician rated depression. In addition, younger patients and those with melancholic depression had higher BDI-II compared to MADRS scores. CONCLUSIONS Results require replication. CONCLUSIONS Self-reported and observer rated depression were only moderately correlated. Researchers and clinicians interpreting the level of depression need to be cognizant of the patient factors that may contribute to either underreporting or overreporting self-report scores relative to observer ratings.