Three instruments for the assessment of quality of life, the Seattle Angina Questionnaire (SAQ), the Short Form Health Survey (SF-36), and the Quality of Life Index-Cardiac Version III (QLI) were administered to 107 patients with stable angina pectoris in a longitudinal randomized trial comparing the use of alternative anginal medications in the management of chronic stable angina pectoris. This study demonstrated that differences in angina severity as measured by the Canadian Cardiovascular Society Classification (CCSC) were related to each of the SAQ subscales, to selected subscales of the SF-36, but not to the QLI. All quality of life (QOL) instruments demonstrated acceptable test-retest reliability when administered over a 2-week interval. Neither the SF-36 nor the QLI were discriminative of angina severity or sensitive to changes in CCSC angina classification. Both the SAQ and QLI detected changes in heart disease related QOL over time.