The prevalence of bipolar disorder is higher than previously believed, especially when bipolar spectrum disorders (BSD) are taken into account, and may approach rates as high as 5%. Difficulties in diagnosing bipolar II and BSD arise from complexities associated with defining and diagnosing hypomania. Additionally, bipolar disorder and BSD are often misdiagnosed because of symptoms that overlap with other psychiatric disorders, particularly unipolar depression. Recognition of the broader spectrum of bipolar disorders and their adequate treatment is paramount because bipolar disorder exacts such a high personal and societal toll, with high rates of suicide and interpersonal problems and a substantial economic burden. Recognition can be improved with active screening, and screening tools such as the Mood Disorders Questionnaire can be easily included in the initial assessment of patients who present with depressive symptoms. Depressive episodes are common in patients who experience BSDs, and increasingly treatment approaches designed specifically for bipolar depression are being studied.