To determine if severity of angina is related to the extent of coronary artery disease (CAD) or prognosis, 341 patients were evaluated by a systematic physician-administered angina questionnaire at entry into a large-scale randomized study of medical vs surgical treatment of stable angina pectoris. Severity of angina was numerically scored; scores were based on frequency of pain, rest pain, amount of daily medication, and level of daily activity. Severity scores were separated into mild, moderate and severe groups of approximately equal numbers and correlated with (1) number of coronary arteries narrowed, (2) presence of left main CAD, (3) ejection fraction less than 50%, (4) abnormalities of left ventricular function, (5) 3-vessel CAD with abnormal left ventricular function, (6) increased heart size by chest x-ray, (7) a noninvasive measure of prognosis, and (8) mortality. Severity of angina was not significantly related to any of the above variables except for the presence of left main CAD (p = 0.046) and increased heart size by chest x-ray (p = 0.001), both of which had low prevalence rates. Severity of angina at baseline was not related to 7-year survival in patients treated medically or surgically. Severity of angina at baseline, however, did predict 1- to 2-year survival in medically treated patients. Similarly, the severity of angina at 1 year and severity at 5 years predicted survival in the subsequent 4 years in the medical group.(ABSTRACT TRUNCATED AT 250 WORDS)