Valve replacement is the most important advance in the management of patients with valvular heart disease, but it cannot be recommended to all patients with valve disease. Cardiac catheterization and angiography, done before surgery, yield valuable and essential information in evaluating these patients. The claim of certain studies that cardiac catheterization and angiography are not needed in these patients cannot be accepted because: The experimental method of these studies was inappropriate; the accuracy and reproducibility of noninvasive techniques in diagnosing the presence and severity of all valve lesions, coronary arterial obstruction, and prosthetic malfunction are not documented; and the studies provide no proof that patients with severe valve disease were not denied surgery, and that patients with mild disease did not have unnecessary operations. Prospective studies that are well designed, well conducted, and scientifically sound are needed. Cardiac catheterization and angiography remain the standard techniques for evaluating patients for valve replacement.