Aneurysms (AN) and pseudoaneurysms are among the complications of vascular access. AN is a focal area of expansion, concentric or eccentric, with the wall consistency the same as all elements of the vessel wall (intima, media and adventitia). Pseudoaneurysm, or false aneurysm, is a blood harvesting without vascular wall, it is characterized by a reactive capsule of connective tissue that delimits it. The K/DOQI guidelines recommend a regular program of monitoring and surveillance of the vascular access. Color-Doppler ultrasound is considered a valuable tool in the preoperative evaluation and in the follow-up. The echo-color-Doppler surveillance plays an important role in diagnosis of aneurysm. It allows monitoring the evolution of the aneurysm, studying vessels walls, thickened because of intimal hyperplasia and to identify the presence of thrombotic material and/or calcification of the wall. Early identification of complications and the adoption of corrective measures will extend the life of the vascular access, with benefit for the patient. Moreover, it will reduce health care costs.