To assess clinical and angiographic outcome after directional coronary atherectomy, the clinical course of 306 patients undergoing this procedure was reviewed. Directional atherectomy was successful in 290 (94.8%) procedures; complications developed in 8 (2.6%) patients. After atherectomy, percent diameter stenosis was reduced from 71 +/- 14 to 14 +/- 14% (p < 0.001) and minimal lumen diameter was increased from 0.87 +/- 0.42 to 2.55 +/- 0.57 mm (p < 0.001). In 128 (42%) patients, adjunct balloon angioplasty was performed to treat either complications or a residual stenosis > 30%. Intravascular ultrasound was also performed in 57 patients after directional atherectomy and demonstrated that a significant amount of residual plaque mass remained in lesions with a calcium arc > or = 90 degrees (17 +/- 5 mm2 vs 12 +/- 5 mm2 in lesions without calcium; p = 0.007). During the 11 +/- 6 month follow-up period, 69 (28.3%) patients developed recurrent clinical events (death, 5; Q wave myocardial infarction, 8; coronary bypass surgery, 31; coronary angioplasty, 36). Using a proportional hazards model, independent predictors of late clinical events included diabetes mellitus (relative risk [RR] = 1.95; p < 0.05), unstable angina (RR = 2.78; p < 0.005) and a prior history of restenosis (RR = 2.21; p < 0.01). We conclude that directional atherectomy is associated with high procedural success rates and infrequent complications in selected lesions subsets, although the degree of plaque resection may be limited if extensive calcium is present. Late clinical events develop in some (28%) patients after directional atherectomy, related to certain preprocedural clinical risk factors.