On the basis of epidemiology, neurobiology and clinical observation, the classification of bipolar disorders has shown considerable development and expansion in recent years. In particular, the recognition of mixed states, the introduction of bipolar II disorders, increasing awareness of the diagnosis of hypomania, as well as the interest in cyclothymic disorders and temperament have led to a shift in diagnostic attitudes in the USA, as well as in European countries. In this article, the possible clinical and scientific benefits of such tendencies are discussed, as are the risks of broadening bipolar disorders beyond DSM-IV. Also demonstrated is how several "modern" concepts of bipolarity have deep roots in the history of German psychiatry; a mixity scale based on Kraepelin's classification of affective mixed states is presented.