The Bypass Angioplasty Revascularization Trial (BARI) is an NHLBI-sponsored multi-centered randomized trial comparing the efficacy of coronary artery bypass sugery (CABG) with percutaneous transluminal coronary angioplasty (PTCA) in patients with stable and unstable manifestations of ischemic heart disease. A variety of endpoints will be assessed including survival, non-fatal myocardial infarction, subjective functional status (angina, heart failure), objective functional status (duration of exercise, ST segment changes, and ejection fraction on rest/exercise radionuclide ventriculogram), and quality of life, including economic status. During a two-year recruitment period, 1800 patients will be enrolled study-wide (approximately 180 from our institution). Eligible patients will be those having angiographic demonstration of at least one major coronary artery with 70% or greater stenosis suitable for both PTCA and CABG plus at least one additional vessel with 50% or more stenosis. A Registry of patients having coronary arteriography for severe or unstable angina will be maintained at each participating institution during the two year enrollment period for the randomized trial. This registry population will provide a valuable documentation of the patient population from which the randomized group were drawn and will help to establish the validity of the observations in the randomized patient population to the broader group of patients undergoing coronary revascularization surgery and PTCA. All patients will be followed for at least four years. The organization of the BARI Trial will include approximately 12 participating clinical units, a Radiographic Core Laboratory, a Data Coordinating Center, possibly a Central Electrocardiographic Laboratory, and possibly a Radionuclide Core Laboratory. The Steering Committee will be composed of principal investigators from the participating clinical units, core laboratories, coordinating center, and NHLBI Project Office. Additionally, a Safety and Data Monitoring Committee composed of experts in relevant statistical and bioethical fields will periodically review the progress of the study and evaluate the results. If BARI can demonstrate that PTCA is as effective as CABG in favorably modifying the endpoints listed above, the impact on current medical practice, as well as the impact on cost containment in the treatment of coronary artery disease will be extraordinarily significant.