Psychotic depression appears to be a distinct illness having a different clinical presentation, history, & prognosis from non-psychotic depression. Both the higher treatent response to the combination of antidepressants & antipsychotics, compared to tricyclic antidepressants used alone, & findings of possible dopaminergic overactivity & noradrenergic underactivity lead to the assumption that the neurobiology of this disorder is distinct as well. Early recognition is critically important.