Directional coronary atherectomy has been introduced as an alternative to conventional balloon angioplasty when treating coronary artery stenoses with complex lesion morphology. To determine the immediate efficacy of coronary atherectomy in patients with such lesions, the first 113 attempts at directional atherectomy in two centres using quantitative angiography were reviewed in 105 patients. The lesions were classified as complex stenosis since 95% had a symmetry index less than 1.0, a length of 6.83 +/- 2.55 mm on average and an area of plaque of 9.77 +/- 6.69 mm2. Procedural success defined as a residual stenosis less than or equal to 50% after tissue retrieval was obtained in 90 (85.7%) of 105 patients. The primary angioplastic success rate, combining atherectomy and balloon angioplasty in case of failed attempt of atherectomy was 95.2%. Coronary atherectomy was unsuccessful in five patients; three were referred for emergency coronary artery bypass grafting. Major complications (death, emergency surgery and transmural infarction) were encountered in 5.7% of the patients. Assessed by quantitative coronary analysis, a residual minimal luminal diameter of 2.42 +/- 0.52 mm and a diameter stenosis of 26 +/- 12% were obtained immediately after directional coronary atherectomy. We conclude that directional coronary atherectomy is particularly suitable for the treatment of stenosis with complex lesion morphology and is associated with acceptable complication rates. Randomized trials comparing atherectomy with balloon angioplasty are warranted to clarify the role of atherectomy in the treatment of lesions in the proximal part of the three major epicardial coronary arteries.