In order to correlate the electrical and mechanical events occurring in atrial flutter, three patients have been studied using the standard electrocardiogram, a computer-processed vectorcardiogram, and reflected ultrasound recordings of valvular motion. Anterior motion of the mitral valve leaflet occurs in the region of the nadir of the atrial flutter wave in lead II of the electrocardiogram. In one patient in whom it was possible to obtain a tricuspid leaflet echocardiogram, anterior motion was also initiated close to the nadir of the flutter wave. The probable sequence of electrical and mechanical events in atrial flutter is discussed. In one patient with a prosthetic mitral valve, correlation of diastolic clicking sounds with respect to the poppet echocardiogram provided some insight into irregularities in timing of previously reported flutter sounds.