This study examines perceptions of coronary heart disease (CHD) risk, associated risk factors, and CHD contributory lifestyles in 80 unaffected siblings of people under 60 years of age with recently documented CHD hospitalizations. Brothers and sisters in the aggregate did not perceive their own high relative risk for CHD nor significantly change their smoking habits, body weight, dietary salt or fat intake, self-reported stress levels, or exercise patterns in the four months following a CHD event in a young index case. They did demonstrate moderate general knowledge; however, specific knowledge about the presence or absence of hypercholesterolemia and hypertension in the index sibling was poor, as documented by comparisons of sibling reports to medical records. This study has implications for risk reduction in this easily identifiable high-risk group, which appears, in the aggregate, to resist lifestyle changes following a CHD event in young brothers or sisters.