Intravascular ultrasound imaging (IVUS) constitutes a new diagnostic technique that provides unique information concerning arterial wall structure and luminal dimensions. To assess the anatomic features of angiographically normal coronary arteries in patients with coronary artery disease, 25 patients (aged 61 +/- 9 years) underwent an IVUS examination before coronary angioplasty. A mechanical (20 MHz) IVUS system was used. Atherosclerotic plaques were identified by IVUS as well-defined structures of variable echodensity protruding into the coronary lumen or disrupting normal coronary wall architecture. Five (20%) patients had minor angiographic irregularities proximal to the target lesion, and all 5 had plaque on IVUS. In the remaining 20 patients the coronary segments proximal to the target lesion were angiographically normal. Of these, IVUS demonstrated the presence of plaque in 16 (80%) patients at 19 different angiographic sites (3 lipidic, 13 fibrotic, 3 calcified). Fifteen plaques had a semilunar appearance and did not disrupt luminal contour, but four clearly protruded into the coronary lumen. Six plaques were located in the left main artery, 4 in the left anterior descending artery, 4 in the left circumflex artery, 4 in the right coronary artery, and 1 in a vein graft. On quantitative angiography, luminal diameter, at sites angiographically normal but with plaque on IVUS, was 3.6 +/- 1 mm. At these sites, both minimal luminal diameter (3.5 +/- 1 mm) and maximal luminal diameter (4.3 +/- 1 mm) on IVUS correlated (r = 0.59 and r = 0.61, respectively) with angiographic measurements (p < 0.05). No complications resulted from the IVUS study.(ABSTRACT TRUNCATED AT 250 WORDS)