Subjective symptomatic improvement is experienced by 90% of patients after coronary bypass surgery. Objective exercise testing reduces this incidence to 70%. An analysis of the multifactorial genesis of pain relief based on data of non-randomized trials reveals that graft patency plays a dominant but not unique role in causing improved symptomatology. In a number of cases, intra-operative myocardial infarctions seem to explain the pain relief but may also have opposite effects. Changes in left ventricular function operate bidirectionally but data on this variable in relation to changes in symptomatology are not amenable for detailed analysis. Progression in native vessel lesions apparently opposes pain relief and has its greatest impact in connection with graft closure. Residual post-operative angina is evidently related also to incomplete revascularization.