Persons with diabetes experience elevated risks of a variety of other illnesses-- including circulatory, visual, neurological, renal, and skin disorders--relative to their nondiabetic peers. Previous estimates of the economic burden of diabetes, however, have not taken full account of this related morbidity and mortality and have therefore understated the cost to the nation due to this disease. Accordingly, we estimated the economic costs of type II, or non-insulin-dependent, diabetes mellitus, reflecting its contribution to the total burden of disease in the United States. In 1986, non-insulin-dependent diabetes mellitus was responsible for $11.6 billion in health care expenditures, including $6.8 billion for diabetic care and $4.8 billion attributable to an excess prevalence of related (principally cardiovascular) conditions. The human toll of non-insulin-dependent diabetes mellitus included 144,000 deaths -- about 6.8% of total US mortality -- and the total disability of 951,000 persons. The total economic burden of non-insulin-dependent diabetes mellitus in 1986, including health care expenditures and productivity forgone due to disability and premature mortality, was $19.8 billion.