This report is the first clinical description of the use of a new low-profile integrated ultrasound-angioplasty catheter (the Oracle Micro, Endosonics Corp.), which has recently been approved by the FDA for routine use during percutaneous transluminal coronary angioplasty (PTCA). PTCA was performed in 44 patients at two clinical sites. With this device, PTCA was accomplished in 47 of 55 (85%) lesions ultimately successfully dilated with balloon angioplasty. No major procedural complications occurred. Adequate ultrasound images were obtained in 51 of 57 lesions (89%). Ultrasound imaging revealed significant morphologic information not apparent by angiography in 51% of imaged lesions and altered the dilatation strategy in 33% of cases. In 10 lesions in which greater inflation pressure or balloon upsizing was performed based solely on an inadequate post-PTCA ultrasound appearance, the minimal lumen diameter further increased from 2.3 +/- 0.3 mm to 2.7 +/- 0.5 mm (P < .001), with no dissections or complications. PTCA may be performed safely in the majority of patients currently undergoing balloon angioplasty with a new low-profile integrated ultrasound-angioplasty catheter. Ultrasound imaging during PTCA provides significant information complementary to angiography and may favorably affect the dilatation strategy of experienced operators.