We like to think of our specialty of interventional cardiology as a scientific one. We practice evidence-based medicine, don't we? Evidence-based implies that we have well-grounded scientific evidence on which to select what we do. That evidence is collated into guidelines that are intended to guide our practice. Some are quoted as having the authority of a religious text and others as mere suggestions. Nonetheless, this reflects what we know about the science of the discipline. But how much of interventional cardiology is science, and how much is art?