A routine method of ascending venography of the lower limb, capable of demonstrating the presence or absence of functioning valves in the deep veins, is described. The technique is given in detail. One rapid and one slow injection of contrast medium are given. Optimum timing for the radiographic exposures has been evolved. The patient performs the Valsalva manoeuvre before the exposure of every film. This causes a reversal of direction of the blood-flow in the veins. The effect of reversing the flow in the veins is described by reference to fluoroscopic and radiographic studies. The appearance of normal and incompetent veins, as shown by this method, are described. The variable anatomy of normal deep veins in the popliteal fossa and thigh is discussed. In addition, the use of this routine method for the demonstration of incompetent communicating veins is advocated. Fluoroscopy has shown that the contrast medium is driven from the deep veins into the incompetent communicating veins during the reversal of t...