Abstract: A method of and apparatus are disclosed for producing alternating pressure in a theapeutic device used to apply compressive forces to a portion of a human body to enhance venous blood flow and prevent venous thrombosis and pulmonary embolism in surgical patients. The apparatus comprises at least two sets of a plurality of inflatable bladders or chambers arranged in alternating relation to one another. All the bladders of one set are inflated and deflated alternately with the deflation and inflation of all the bladders of the other set to produce a therapeutic alternate chamber pumping action on that portion of the body being treated. A single fluidic flip-flop device controls the supply and venting of pressurized fluid to and from the chambers.