Pulmonary venous flow, pressure, and diameter were recorded in dogs recovered from implantation of monitoring devices. Flow patterns in pulmonary veins were similar to those in vena cavae. Left atrial systole produced a regurgitant wave in flow and an increase in pressure and diameter of the pulmonary vein. Ventricular systole was associated with a rapid increase in venous flow and a decrease in vein diameter; a 2nd, larger increase in flow occurred during ventricular diastole. No consistent pressure pulse accompanied these forward flow pulsations. The usual effect of inspiration was augmentation of venous flow. Positive flow pulses were recorded during ventricular systole from the right pulmonary vein of an animal whose right lung was perfused entirely by the superior vena cava. It is concluded that attraction into the heart is more important in determining venous flow patterns than transmitted forward flow pulses.