This article argues for the necessity of a partial return to Kraepelin's broad concept of manic-depressive illness, and proposes definitions--and provides prototypical cases--to illustrate the rich clinical phenomenology of bipolar subtypes I through IV. Although considerable evidence supports such extensions of bipolarity encroaching upon the territory of major depressive disorder, further research is needed in this area. From a practice standpoint, the compelling reason for broadening the bipolar spectrum lies in the utility of mood stabilizers as augmentation or monotherapy in the treatment of major depressive disorders with soft bipolar features falling short of the current strict standards for the diagnosis of bipolar II and hypomania in DSM-IV and ICD-10.