ABSTRACT: The concept of ideal cardiovascular health (CVH), defined by the American Heart Association primarily for coronary heart disease and stroke prevention, may apply to diabetes mellitus prevention among blacks.Our sample included 2668 adults in the Jackson Heart Study with complete baseline data on 6 of 7 American Heart Association CVH metrics (body mass index, healthy diet, smoking, total cholesterol, blood pressure, and physical activity). Incident diabetes mellitus was defined as fasting glucose ?126 mg/dL, physician diagnosis, use of diabetes mellitus drugs, or glycosylated hemoglobin ?6.5%. A summary CVH score from 0 to 6, based on presence/absence of ideal CVH metrics, was derived for each participant. Cox regression was used to estimate adjusted hazard ratios. Mean age was 55 years (65% women) with 492 incident diabetes mellitus events over 7.6 years (24.6 cases/1000 person-years). Three quarters of participants had only 1 or 2 ideal CVH metrics; no participant had all 6. After adjustment for demographic factors (age, sex, education, and income) and high-sensitivity C-reactive protein, each additional ideal CVH metric was associated with a 17% diabetes mellitus risk reduction (hazard ratio, 0.83; 95% CI, 0.74-0.93). The association was attenuated with further adjustment for homeostasis model assessment for insulin resistance (hazard ratio, 0.89; 95% CI, 0.79-1.00). Compared with participants with 1 or no ideal CVH metric, diabetes mellitus risk was 15% and 37% lower in those with 2 and ?3 ideal CVH metrics, respectively.The AHA concept of ideal CVH is applicable to diabetes mellitus prevention among blacks. These associations were largely explained by insulin resistance.