The prevalence and diversity of bipolar disorder may be under appreciated. Recent data suggest that when clinicians look beyond strict DSM-IV criteria for bipolar disorder, we find that as many as 5%-7% of the general public may suffer from some form of "bipolar spectrum disorder." At the same time, the comorbidity between bipolar disorder and other psychiatric conditions may create understandable confusion in diagnosis and treatment. Recognition of bipolar depression and the "soft end" of the bipolar spectrum demands not only the identification of the hallmarks of bipolarity, but a heightened awareness of the problems of missed diagnosis and inappropriate treatment. By attending to some key historical and clinical clues, the psychiatrist is more likely to detect bipolar spectrum disorder and provide appropriate treatment for it.