To characterize the changes in indications for coronary angiography we compared indications and therapeutic conclusions of cardiac catheterization, including coronary angiography, in 100 consecutive patients in 1975 and 100 consecutive patients in 1985. The baseline characteristics of the patients in the two groups were similar, except for age (50 +/- 10 vs 56 +/- 9 years, p less than 0.0001) and prior angioplasty (0 vs 12, p less than 0.0001). The main indications for coronary angiography in the two groups were (1975 vs 1985) chest pain in 67 vs 62 (n.s.), myocardial infarction in 10 vs 17 (n.s.), prior coronary surgery in 3 vs 0 (n.s.), major arrhythmias in 1 vs 1 (n.s.), and incidental (coronary pathology not the primary issue) in 19 vs 8 (p less than 0.05). We further analyzed each of the main indications in the two groups. Chest pain: angina ruled out in 21% vs 26% (n.s.), stable angina 64% vs 61% (n.s.), unstable angina 15% vs 13% (n.s.), positive non-invasive tests 39% vs 44% (n.s.). Myocardial infarction: acute intervention 0 vs 12% (n.s.), angina after infarction 20% vs 47% (n.s.), positive non-invasive tests after myocardial infarction 20% vs 41% (n.s.). Incidental: valvular heart disease 57% vs 63% (n.s.), cardiomyopathy 26% vs 13% (n.s.), congenital heart disease 11% vs 0 (n.s.), aortic dissection 5% vs 25% (n.s.), other 5% vs 0 (n.s.). Overall, clinical suspicion of coronary artery disease was confirmed and documented in 80% (65/81) vs 77% (61/79) of patients (n.s.), and normal coronary arteries were found in 20% (16/81) vs 23% (18/79) of patients respectively.(ABSTRACT TRUNCATED AT 250 WORDS)