This preliminary report deals with the direct radiographic study of discrete, relatively small spots of artificial radiopacity during their passage through the cardiovascular structures and offers a new and promising technic for studying the motion of blood. As used here, motion refers to movement of and within the blood stream. So defined, it is fundamental to the subject-matter of hemodynamics. Continuing studies are focused upon two major hemodynamic parameters: 1. The velocity, acceleration and deceleration of circulating blood. Through appropriate specialized radiographic technics, it is possible to measure the movement of blood as a function of time. Observations may be completed in 1 msec., repeated in rapid sequence and made simultaneously at many different points within the cardiovascular system. 2. Flow characteristics of circulating blood. The graphic study of flow patterns at multiple points within the blood stream can be carried out simultaneously with blood velocity observations. By analogy, in this technic the blood vessels and chambers of the heart serve as wind tunnels; the blood is the wind, the spots of opacity are smoke tracers and the myocardium is the source of power. The results of extensive experimental studies indicate that the above goals are achievable and warrant the considerable effort and costs involved. It is hoped that this preliminary report will encourage others to explore the possibilities of the method and thereby hasten its perfection.