During the first year a mailed questionnaire was designed which provided baseline data on family history, body size, morbidity, psychosocial characteristics, smoking, alcohol consumption, diet, physical activity, and drug use. The baseline data were used for analysis of cardiovascular, pulmonary, and blood diseases, and for follow-up. From the original survey, the Veterans Administration provided magnetic tape data on zygosity, smoking, alcohol consumption, heart, lung, and blood diseases, discharge rank, education, occupation, and family income. The questionnaire was completed by almost 8,900 individuals including over 3,000 twin pairs.