In order to estimate forward stroke volume (FSV) and mitral regurgitant volume (MRV) by echocardiography, the relationship between FSV or the severity of mitral regurgitation (MR) determined by conventional methods and those measured by aortic-left atrial echogram was investigated in 119 subjects, consisting of 88 patients without MR (no-MR group) and 31 patients with MR (MR group). The most adequate echocardiographic measurement for estimating FSV in the no-MR group was the product of posterior aortic wall excursion (Ao-PWE) and left atrial dimension (LAD); i.e., Ao-PWE X LAD. Further sophistication in estimating FSV was achieved by separating the subjects with LAD smaller than or equal to 40 mm from those with LAD > 40 mm. MRV was estimated by subtracting the FSV determined directly by either Fick or thermodilution method from the stroke volume determined by echocardiography. MRV so obtained was compatible with the severity of MR determined by LV cineangiography. The FSV in the no-MR group and the MRV in the MR group could be estimated with reliable accuracy by echocardiography alone (in the former) and by echocardiography plus a simple procedure such as Fick or thermodilution method (in the latter). Furthermore, this method was found to be free of influence from left ventricular dyssynergy or aortic regurgitation.