Since the advent of the psychopharmacological revolution, manic-depressive illness (bipolar disorder) has served as a principal point of focus for modern psychiatric research. Today, although the accumulation of knowledge about this illness and its treatment constitutes one of the extraordinary success stories of modern biomedical science, it remains in many ways a paradox—a paradox because, despite all we know, the illness too often is unrecognized or misdiagnosed, and inappropriately or ineffectively treated. The disparity between optimal care, on the one hand, and what is routinely provided, on the other, is perhaps nowhere larger than in manic-depressive illness. Its human and economic impact remains excessive.