It has been shown that systolic excursion of the mitral annulus (MA) correlates well with left ventricular (LV) systolic function. Evaluation of the complicated shape and dynamics of the mitral annulus, however, may require rigorous methodology. The aim of this study was to investigate differences in MA motion between hypertrophic cardiomyopathy (HCM) and left ventricular hypertrophy (LVH) patients due to hypertension or aortic stenosis using real time three-dimensional echocardiography (RT3DE). We studied 10 HCM, 10 LVH, and 10 controls. Mean MA area changes between early and late systole were 9.5 +/- 4.3% in HCM, 26 +/- 15% in LVH and 19 +/- 10% in normal controls. MA apicobasal motion was 5.8 +/- 4 mm in HCM, 11 +/- 4 mm in LVH, and 13.6 +/- 6 mm in normal controls. RT3DE with digital reconstruction of MA accurately display complicated MA geometry and dynamics during a cardiac cycle. Annular function in LVH was similar to that of the normal group while annular apicobasal motion and area changes were reduced in HCM.