Historically, morbidity and mortality have been the primary outcome measures in coronary artery bypass research. Limited health care resources have led to greater emphasis on cost as a primary outcome mea sure. These are each important measures, but they fail to directly assess what patients care about, which is their overall quality of life (QOL). When QOL is used as an outcome in medical research, it should encompass at a minimum the following domains: physical status, mental function, social interaction, and disease-specific measure. Fortunately, QOL assessment instruments already exist that are reliable, valid, and sensitive to change. This article describes how QOL is defined, what instruments are available, how they have been devel oped, and how they are selected. Next, QOL in the coronary artery bypass literature is reviewed. This in cludes both the large randomized trials as well as studies focusing solely on QOL. Finally, future directions for QOL as an outcome measure are examined.