Pulsus paradoxus is associated with many clinical conditions and is defined as a greater than 10 mm Hg end-inspiratory decrease in systolic blood pressure. Kussmaul's original definition of pulsus paradoxus is presented, along with an explanation of his choice of the term "pulsus paradoxus." A case of pulsus paradoxus is graphically described using simultaneous two-dimensional targeted M-mode, Doppler echocardiographic, and high-fidelity pressure recordings.