In order to determine the rate of progression in valvular heart disease, the records of patients with simple valve lesions and two cardiac catheterizations performed prior to surgery were examined retrospectively. In 53 patients (mitral regurgitation n = 16, aortic regurgitation n = 13, mitral stenosis n = 13, aortic stenosis n = 11) complete data were available. The time interval between the two studies averaged 47 +/- 24 months. In patients with mitral regurgitation left ventricular ejection fraction deteriorated significantly faster than in the other groups; the rate of left ventricular volume gain and rise in pulmonary pressure also tended to be higher in this group. The transvalvular gradient in aortic stenosis showed a highly significant increase during the observation period (56 +/- 26 mm Hg vs 78 +/- 29 mm Hg; p less than 0.01), however, left ventricular ejection fraction remained within normal limits. These data indicate that patients with mitral regurgitation should be followed closely prior to valve replacement.