Background: Despite increasing knowledge about degree and distribution pattern of intimal hyperplasia in cardiac allograft vasculopathy, coronary artery remodeling is only poorly understood in this disease. Methods: To evaluate vascular geometry, intravascular ultrasound was used to characterize 57 advanced lesions in 35 consecutive transplant recipients. Lumen, plaque, and vessel area in these target lesions were compared with proximal and distal reference sites. Results and Conclusions: Vascular remodeling by compensatory local vessel enlargement (positive remodeling) and circumscript vascular constriction (negative remodeling) could be demonstrated. Plaque area in stenotic lesions was significantly increased compared with the mean reference site (5.6 ± 3.0 mm² versus 2.8 ± 1.5 mm², p < 0.001); however, inadequate compensatory enlargement rather than intimal hyperplasia was shown to be the most important predictor of luminal obstruction (r = 0.77, p < 0.001). (Am Heart J 1998;135:628-33.)