SummaryX rays showing esophagal retrodeviation in mitral disease are only slighty different whether taken during systole or diastole. On the other hand, the posterior incurvation of the esophagus is markedly increased when the patient is lying on his side. It may appear in this position when it was missing in the standing patient. This technic is indicated whenever the other elements of mitral cardiopathy are insufficient to establish the diagnosis.