The widespread use of the Swan-Ganz catheter is a result of a general misconception. It is widely accepted that the collection of data is a way of practicing scientific medicine. That is simply not true. The data must on balance contribute to a better outcome for patients as established by a scientific trial. The present widescale use of the catheter provides a striking example of the misuse or even mindless use of technology. Because of a tenuous risk-benefit balance, it is not at all certain that the general use of the Swan-Ganz catheter is justifiable and its use at best is semi-scientific. A reasonable approach would be to suspend its use pending an appropriate clinical trial which established safety and efficacy. Although the prospects for a clinical trial are bright, the prospects for a moratorium are not at all bright. While awaiting the results of an appropriate trial, individual physicians should only use the catheter when the probability is high that the data obtained by its use will provide more effective decision making. Such an approach by itself should result in a near-moratorium. Its present use is not a form of scientific medicine but at best a form of semi-scientific clinical practice.