When assessing a patient with depression it is crucial not to miss a diagnosis of bipolar depression. In this review we suggest that it can be achieved, first, by consistently usingstandardised diagnostic criteria (e.g., DSM-IV-TR or ICD 10) and, second, by ascertaining the presence of some clinical features. The latter include previous episodes of mood elevation, current or past episodes of psychotic depression, onset of recurrent depressive disorder before the age of 25, a strong family history of mood disorder and suicide, lack of response or "wearing off" of response to well conducted antidepressant treatment, and an unusually fast response to antidepressants with features of elation. Although more and better research is required to establish the validity, sensitivity, specificity, and predictive value of each one of these features we suggest that from a practical point of view they would increase clinicians' awareness of bipolar depression.