The NHLBI is currently supporting part of NHANES IV. NHANES IV is a study of a representative sample of approximately 30,000 of the non-institutionalized population of the United States, obtained through the use of a complex multi-stage sampling design using a combination of health questionnaire and physical exam. Each single year and any combination of consecutive years comprises a nationally representative sample which will facilitate linkage to other surveys that provide yearly estimates such as the Continuing Survey of Food Intake by Individuals and allow limited national estimates from NHANES IV each year. The NHLBI component obtains information on the prevalence and distribution of common heart, vascular, pulmonary and blood diseases. The core questionnaire is based on the Health Interview Survey (HIS), and provides information on disease, risk factors, and components of medical care. Through the use of a Mobile Exam Center (MEC), subjects throughout the country are administered a standardized physical exam to obtain data on blood pressure, venipuncture, spirometry, congestive heart failure (CHF), and ankle-arm blood pressures. Sub-populations of the U.S. of particular interest, including minorities and age groups of particular concern like the very young and the elderly, will be over-sampled. Specific objectives of NHANES IV include: ascertaining the prevalence of common heart, vascular, lung, and blood disease in a representative sample of the non-institutionalized population of the United States; estimating the frequency and distribution of known and suspected risk factors for these heart, vascular, lung, and blood disease; measuring associations between risk factors and diseases; ascertaining the frequency and distribution of medical, surgical, pharmacologic, and behavioral interventions used to prevent or treat heart, lung and blood diseases; measuring trends over time in heart, lung and blood diseases and risk factors; relating clinically manifest disease, risk factors, and components of medical care detected at the baseline examination to subsequent morbidity and mortality (detected by follow-up questionnaires and matching with the National Death Index); determining the extent to which findings in NHLBI populations-based epidemiological studies reflect national data and may be generalized to the U.S. population. A Central Lipid Laboratory will be established to: standardize for lipid measurements; accurately measure total cholesterol and HDL cholesterol for the entire NHANES IV sample population; and accurately measure triglycerides for the fasting NHANES IV population.