We report two patients undergoing peripheral percutaneous transluminal angioplasty in whom angiography, angioscopy, and ultrasound imaging were performed before and after balloon angioplasty. The first case with smooth atheroma diagnosed by angiography was found to have unrecognized partially occlusive thrombus by angioscopy. After angioplasty, an intimal tear was identified by angioscopy and ultrasound but it was not seen by angiography. The intravascular ultrasound image showed the tear to extend to the adventitia. In the second case, an apparently smooth intimal surface as imaged by angiography was found by angioscopy and ultrasound to have extensive damage, including subintimal hemorrhage, intimal flaps, and arterial dissection at the angioplasty site. These data suggest that the type of information derived from the three imaging techniques is quite different, and that each may have a specific role in intravascular diagnosis.