To describe how often a right heart catheterization was performed at the time of coronary angiography, the patient characteristics that predicted the use of this procedure, and the variation among cardiologists in the use of this test, we reviewed all cases of coronary angiography (n = 1,282) during the first 2 mo of 1993 at two large community hospitals. Fifty-two percent of the cases received a right heart catheterization at the time of their coronary angiography. The following characteristics were associated with the receipt of a right heart catheterization in a logistic regression analysis: cardiomyopathy (odds ratio = 2.59, 95% CI = 1.01, 6.62), congestive heart failure (odds ratio = 2.07, 95% CI = 1.42, 3.01), valvular heart disease (odds ratio = 2.54, 95% CI = 1.44, 4.49), no coronary angioplasty performed at the procedure (odds ratio = 2.71, 95% CI = 2.12, 3.45), and increased age (odds ratio = 1.13 per decade, 95% CI = 1.03, 1.25). Of 37 cardiologists who performed > 10 coronary angiography procedures, the use of right heart catheterization varied from 10-90%. The cardiologists' practice variation persisted after adjustment for patient clinical characteristics. Because of the high utilization of right heart catheterization at the time of coronary angiography and the variation in use among cardiologists, even when controlling for patient characteristics, the issue of appropriate indications for this procedure needs to be addressed in a rigorous fashion.