Two-thirds of all deaths in developed countries are caused by the major noncommunicable diseases, e.g., cardiovascular disease, cancer, and non-insulin-dependent diabetes mellitus (NIDDM). There is increasing evidence that these diseases are a consequence of life-style change, and they have a number of risk factors in common. Primary prevention of both insulin-dependent diabetes mellitus (IDDM) and NIDDM has become increasingly important because of their significant morbidity and mortality and the human and economic costs associated with diabetes and its complications. Prevention of the two major forms of diabetes, IDDM and NIDDM, are quite separate issues. The former appears to be an autoimmune disorder, whereas the latter should be considered along with other life-style-related noncommunicable diseases. The primary prevention of NIDDM appears to offer the greatest promise of success. The uncertainty that still exists as to the role of obesity and other risk factors in the development of NIDDM gives support to a multiple-risk-factor intervention approach (through a healthy life-style strategy) for NIDDM prevention.