Interviews with a probability sample of 617 adults in the Chicago area indicated widespread lack of information about major probable causes of heart attacks in persons younger than 60 years: 28% named cigarette smoking, 21% named high blood pressure, and 13% named cholesterol or fat in the diet or blood. Half did not name any of these risk factors, and only 1% named all three. Although three fourths believed that heart attacks are preventable, few named specific behaviors that would effectively reduce risk factors other than smoking. Sustained community-wide educational programs about reducing coronary risk factors are clearly needed and can be effective.