Many patients present to a primary care setting with symptoms of a mood disorder. These symptoms may be indicative of an anxiety disorder or a depressive disorder, but they may also represent bipolar disorder, which is more common than many practitioners think. Correctly diagnosing bipolar disorder can be complex, because patients tend to seek treatment when they are experiencing the symptoms of depression or anxiety rather than mania or hypomania. Comorbid disorders such as substance abuse and anxiety disorders may complicate the clinical presentation. Failing to correctly diagnose bipolar disorder can have serious consequences in terms of patients' morbidity and mortality, quality of life, and financial costs.