Major findings from the study include: in 1985, total economic costs of alcohol abuse, drug abuse, and mental illness (ADM) was approximately $218.1 billion; mental illness accounted for 48 percent of the total costs, followed by alcohol abuse (32 percent) and drug abuse (20 percent); direct treatment and support costs accounted for 24 percent of the total, followed by morbidity costs (37 percent) and mortality costs (16 percent); and core costs (costs directly related to the treatment and support of persons with ADM disorders) amounted to $168 billion in 1985, with mental illness accounting for 59 percent, alcohol abuse accounting for 35 percent, and drug abuse accounting for 6 percent. This report presents the results of a study to measure the possible economic costs to society due to ADM disorders. The study had four primary objectives: measure the possible economic costs to society due to ADM disorders by estimating the economic costs for 1985; update previous cost estimates on the basis of comprehensive data sources and improved methodology; develop an improved methodological approach to deal with the important issues of comorbidity and overlap of ADM disorders; and conduct a review of the literature on the economic costs of illness, with emphasis on studies related to ADM. Tables, figures, references, and appendixes