Cardiovascular diseases, which include coronary heart disease, account for 48% of deaths in Europe and many developed countries have specifically targeted significant reductions in coronary heart disease deaths as major health care objectives. Reduction in the death rate and morbidity from coronary heart disease can be accomplished through three primary interventions: (1) modification of lifestyle behaviors; (2) use of medications; and (3) surgical procedures. In order to prescribe a specific intervention, patients with heart disease are typically diagnosed by physicians with one or more of three inter-related (but clinically distinct) conditions: myocardial infarction, angina pectoris, or heart failure. This diagnostic conceptualization of coronary heart disease has led to important improvements in specific treatments and researchers have increasingly focused their attention on comparing the efficacy of one intervention versus another. Patients, providers, and researchers have increasingly become interested in identifying those interventions that not only improve mortality but also improve symptoms, function, and health-related quality of life. Thus, researchers have developed specific symptom scales and health-related quality of life instruments for each of these three coronary heart disease conditions for use in clinical trials. As part of the Euro Cardio-QoL Project, the HeartQoL study is designed to develop a single reliable and valid core coronary heart disease-specific, health-related quality of life questionnaire, to be called the HeartQoL, in order to compare outcomes with the same or across different treatments among pure or mixed populations of patients with myocardial infarction, angina pectoris, and/or heart failure. To be of value in international studies, health-related quality of life instruments must be available in a range of languages as many important clinical studies require multi-national and multi-language site collaboration. The project will recruit a total of 4200 patients with myocardial infarction (n=1400), angina (n=1400), and heart failure (n=1400) in 40 sites located in 15 countries where 13 different languages are spoken. Data will be collected using a battery of three valid self-administered, health-related quality of life instruments at baseline and again within 2 to 4 weeks to develop the core HeartQoL questionnaire and to establish its reliability. Anxiety, depression, mood, personality, and generic health-related quality of life will also be assessed at baseline to provide preliminary evidence of validity.