The aim of this study was to determine the effect of intravascular ultrasound (IVUS) imaging on decision making in the performance of coronary interventions. One hundred lesions were assessed in 87 patients undergoing balloon or laser angioplasty, atherectomy, stent placement, and additional diagnostic examination. Angiographically acceptable results were deemed inadequate by IVUS in 29% of angioplasties and 30% of stent deployments, and planned procedures subsequently were altered. Abnormalities commonly identified by IVUS and not by angiography were 13 coronary dissections after the procedure and 14 significant stenoses in apparently normal angiograms and significant stenoses were excluded in 7 patients with ambiguous angiograms. The apparent contribution of coronary IVUS imaging led to its significantly increased use over a 1-year period, as coronary interventional decisions on the basis of IVUS findings increased from 4 (17%) of 19 to 60 (74%) of 81. These data suggest that IVUS is a useful adjunct to angiography in selected patients for (1) identification or exclusion of dissection, (2) assessment of the adequacy of balloon angioplasty, (3) identification or exclusion of thrombus, (4) measurement of the depth of tissue removal, (5) determination of stent size and the result of stent deployment, and (6) assessment of the severity of stenoses, especially at ostial sites.