Although encouraging initial results have been demonstrated after directional atherectomy, the mechanisms and predictors of late lumen loss and restenosis after this procedure have not been evaluated. To examine these issues, clinical and angiographic follow-up were obtained in 262 (96%) and 212 (77%) of 274 patients undergoing successful directional coronary atherectomy. Symptom recurrence developed in 87 (33%) patients and angiographic restenosis was found in 93 (44%). Restenosis was highest in re-stenotic lesions in saphenous vein grafts (78% [95% confidence interval (CI): 56 to 100%]) and lowest in new-onset lesions in the left anterior descending (27% [95% CI: 15 to 39%]) and circumflex (14% [95% CI: 0 to 43%]) coronary arteries. Residual lumen diameter immediately after atherectomy was smaller in re-stenotic lesions (p = 0.002) and in lesions > or = 10 mm in length (p = 0.02). Late lumen loss was associated with the minimal lumen diameter immediately after atherectomy (p < 0.001), saphenous vein graft lesion location (p = 0.008), and male gender (p = 0.02). Re-stenotic lesions (p < 0.001), lesions > or = 10 mm in length (p = 0.018), saphenous vein graft lesion location (p = 0.025) and male gender (p = 0.045) were independent predictors for restenosis. It is concluded that restenosis after directional atherectomy is related both to factors resulting in a suboptimal initial result and to factors contributing to excessive late lumen loss. These results may have implications for lesion selection in patients undergoing directional coronary atherectomy.