An angiocardiographical analysis of the rheumatic mitral valvular changes was performed on 344 patients examined during the period from October, 1977 to July, 1980. The following results were obtained: 1) In the analysis of the mitral apparatus, the mitral orifice projection which enables us to observe the mitral annulus as en face and the long axial projection enabling us to observe the profile was particularly useful for the diagnostic validity. 2) Mitral orifice projection was useful for the diagnosis of stenosis dominant lesion, while long axial projection was beneficial for the diagnosis of regurgitation dominant lesion. 3) The measurements of mitral apparatus were carried out through these projection methods. It was found that the diameter of annular ring as well as the area of posterior leaflet were markedly increased in the mitral regurgitation group.