The echocardiographic findings of six patients with pure mitral stenosis associated with pure aortic stenosis were compared with the findings from a series of ten cases of pure aortic stenosis without mitral disease. Each patient also underwent haemodynamic studies in order to quantitate the severity of the stenoses. The aortic stenosis was of the same degree of severity in both series (0.71 +/- 0.24 cm2 and 0.73 +/- 0.16 cm2). The systolic separation of the aortic valve was greater than 1 cm in 4 of the 6 cases on echocardiography, corresponding to a false negative of tight aortic stenosis. This appearance corresponded to a doming of the aortic valve on 2D echocardiography. The wall thickness was significantly less in the AS + MS series than in pure SA series (1.13 +/- 0.13 cm compared with 1.52 +/- 0.21 cm; p less than 0.01). The wall was found to be thicker, the tighter the MS. Overall, the diagnostic criteria of the severity of AS on echocardiography (restricted opening of the valve and the severity of ventricular wall hypertrophy) were absent in the association of AS + MS. The absence of myocardial hypertrophy can not be fully explained. It could be related to a decreased filling on the left ventricle and therefore a smaller systolic ejection volume because of the mitral obstruction.