The Simpson atherectomy device was used to treat 12 intragraft stenoses, six complete subclavian vein occlusions, and 14 venous outflow stenoses in 24 patients undergoing hemodialysis. Patients were followed up clinically and by means of venography at approximately 1, 3, 6, 9, and 12 months after treatment. Twenty-eight atherectomy specimens were examined histologically. Twenty-six (81%) of 32 lesions were treated with initial technical success. Including technical failures, seven (58%) of 12 intragraft stenoses are angiographically patent at a mean of 5.0 months and five (50%) of 10 are clinically patent at 6 months. Three (50%) of six subclavian veins are angiographically patent at a mean of 5.6 months, and four (67%) of six are clinically patent at 6 months. Three (21%) of 14 venous outflow stenoses are angiographically patent at a mean of 5.0 months and five (38%) of 13 are clinically patent at 6 months. Histologic examination showed neointimal fibromuscular hyperplasia in 26 of 28 lesions. When 30% or less angiographic residual stenosis is used as the criterion for initial technical success, directional atherectomy appears to be effective therapy for intragraft stenoses and, with balloon angioplasty, for some catheter insertion-related subclavian occlusions. Directional atherectomy appears to have a recurrence rate for venous outflow stenoses similar to that for balloon angioplasty when the same criterion is used.