Studying an elderly cohort confers several special advantages compared to younger or mixed-age populations. Atypical features described in this chapter include: late age of onset, prolonged latency from first depression to first mania, high prevalence of neurologic comorbidity presence of cognitive impairment, and poor outcome characterized by increased mortality. Age of onset can be an important variable that distinguishes subtypes of mania and bipolar disorder in order to improve understanding of underlying pathogenesis. Retrospective cohort studies of mania in late life have established a very clear association between bipolarity in old age and a heterogeneous group of neurological disorders. While pharmacokinetic and pharmacodynamic factors dictate a significant alteration in dosage, the general approach to treatment of bipolarity is not fundamentally different in an elderly population. The narrow therapeutic range for pharmacological therapies in old age is an important consideration in ongoing management.