Distal protection devices have been proved to decrease distal embolization and improve outcome in unselected patients undergoing percutaneous coronary intervention (PCI) in saphenous vein grafts (SVGs). However, it remains uncertain whether distal protection is necessary in all patients. We investigated whether clinical or angiographic variables can predict distal embolization and, hence, need for a distal protection device. Fifty-eight consecutive SVGs that underwent PCI with a FilterWire distal protection device were studied. After the procedure, the FilterWire was fixed in formalin and photographed, and embolic debris area (square millimeters) was quantified by semi-automated edge-detection analysis. Debris area was correlated with 6 prespecified variables: clinical presentation, SVG age, reference lumen diameter, plaque volume, SVG degeneracy, and presence of a filling defect. Embolic debris was identified in 57 of 58 grafts (98%). Median debris area was 4.0 mm(2) (range 0.0 to 25.1). None of the prespecified variables predicted the occurrence of distal embolization or the amount of captured embolic debris. In conclusion, distal embolization during SVG PCI is universal. Embolic burden cannot be predicted by clinical or angiographic variables, and embolic protection should be used in all patients.