To define the immediate and long-term success of directional coronary atherectomy (DCA) in patients with total coronary occlusions, DCA was performed in seven patients with coronary occlusion duration of 41±40 days (range, 5 to 105). Procedural success, defined as an improvement in percent diameter stenosis of greater than or equal to 20%, residual diameter stenosis of less than or equal to 50%, and the absence of in-hospital complications, was obtained in six (86%) of seven patients. With quantitative angiography, a residual minimal luminal diameter of 2.3±0.9 mm and diameter stenosis of 32%22% were obtained immediately following DCA. In the one procedural failure, angiographically detectable coronary calcification prevented effective atheroma resection. In four patients with primary procedural success, repeated coronary arteriography was performed 5.8±0.7 months following DCA. At the time of the follow-up study, all vessels remained patent with a residual diameter stenosis of 34%17% (range, 18% to 50%). Histologic analysis, with quantitative methods, demonstrated that the excised specimen contained lesions that were 23%12% fibrocellular, 30%20% sclerotic, and 11%7% atheromatous. Additionally, fresh or organizing thrombus was present in all specimens. Whereas some component of vessel wall was excised in four of seven patients, adventitia was obtained in only two. We conclude that directional atherectomy can be successfully performed in patients with total coronary occlusions and that thrombus is a significant component. Our pilot findings of long-term success in debulking coronary arteries that have been chronically occluded are encouraging and require investigation in much larger series of patients.