In 1991, the costs for manic-depressive illness, which has a lifetime prevalence of 1.3% among adult Americans, totaled $45 billion. Costs were broken down into their direct and indirect components. Direct costs totaling $7 billion consist of expenditures for inpatient and outpatient care, which are treatment related, as well as nontreatment-related expenditures such as those for the criminal justice system used by individuals with manic-depressive illness. Indirect costs, which were $38 billion, include the lost productivity of both wage-earners ($17 billion) and homemakers ($3 billion), individuals who are in institutions ($3 billion) or who have committed suicide ($8 billion), and caregivers who take care of manic-depressive family members ($6 billion). The method for determining each expenditure is provided, and the implications of these staggering costs are discussed. These calculations rely heavily on methods and data bases that were developed for the accompanying paper on the costs of schizophrenia.