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Background Recently, long-term constriction of the vessel has been suggested as an alternative mechanism of restenosis after coronary angioplasty. Methods and Results To understand remodeling of human coronary arteries undergoing coronary angioplasty or atherectomy, serial intravascular ultrasonographic examinations were performed at preintervention and postintervention examinations and at 24 hours, 1 month, and 6 months. Complete serial data were obtained in 61 lesions (balloon angioplasty, 35 lesions; directional atherectomy, 26 lesions). Lumen area improved from 6.81±2.24 mm 2 after intervention to 8.22±2.79 mm 2 at 1 month ( P =.0001) and decreased to 4.88±2.86 mm 2 at 6 months ( P =.0001). Vessel area enlarged from 17.32±5.35 mm 2 after intervention to 19.39±5.33 mm 2 at 1 month ( P =.0001) and decreased to 16.33±5.54 mm 2 at 6 months ( P =.0001). Plaque+media area increased significantly from postintervention examination to 24 hours (10.51±4.38 versus 10.96±4.49 mm 2 , P =.0008) and from 24 hours to 6 months (10.96±4.49 versus 11.45±4.45 mm 2 , P =.03). Changes in lumen area in each study interval correlated more closely with changes in vessel area than with changes in plaque+media area. Restenotic lesions compared with nonrestenotic lesions had a greater decrease in the vessel area between 1 month and 6 months (−4.33±2.73 versus −2.49±2.15 mm 2 , P =.006) and greater increase in the plaque+media area both within 24 hours (0.84±1.22 versus 0.27±0.38 mm 2 , P =.04) and between 24 hours and 6 months (1.19±2.19 versus 0.18±1.46 mm 2 , P =.04). Conclusions Remodeling after coronary angioplasty or atherectomy was characterized by early adaptive enlargement and late constriction of the vessel.