To determine the extent to which the Fifth Joint National Committee on Detection, Evaluation, and Treatment of High Blood Pressure (JNC-V) guidelines were implemented in high-risk families with premature coronary heart disease, we examined the prevalence of hypertension and associated coronary risk factors in asymptomatic siblings of persons with documented premature coronary disease (<60 years of age). A total of 859 apparently healthy siblings (51% male, 19% African American) were screened for coronary risk factors. Siblings were classified as normotensive or hypertensive (BP > or = 140/90 and/or current antihypertensive pharmacotherapy). The prevalence of hypertension, awareness, treatment, and control among siblings was compared with published national estimates from the third National Health and Nutrition Examination Survey. The prevalence of hypertension in siblings was 44%. Among all hypertensives, only 60% were aware of being hypertensive, 45% were being treated, and 16% were under control. A high prevalence of other coronary risk factors was found among hypertensive siblings: 72% were hypercholesterolemic; 61% were obese; 29% were current smokers; 82% were consuming >30% of calories from fat; and only 14% were participating in vigorous physical activity three or more times per week. Comparisons with the national reference population revealed siblings to have a significantly higher prevalence of hypertension, along with significantly lower levels of awareness, treatment, and control. These findings demonstrate the intersection of multiple risk factors among hypertensive siblings and emphasize the need for more aggressive screening and treatment in this easily identifiable high-risk population.