The neurofibromatoses are a heterogeneous set of genetic disorders having clinical manifestations that involve the skin, the nervous system, or both. In addition, the disease can be confounded by a broad spectrum of complications, such as various kinds of osseous lesion, vascular lesions, aqueduct stenosis, optic glioma, and learning disabilities. Neurofibromatosis results in vascular involvement in approximately 10% of cases. Stenotic lesions predominate, but aneurysms have been documented as well. Rarely noted, however, have been peripheral aneurysms. In this report, we discuss the case of a 66-year-old woman with type 1 neurofibromatosis and a popliteal artery aneurysm who was operated upon because of threatened limb ischemia. Histological findings confirmed neurofibromatous invasion of the vessel wall.