Background: Dialysis access occlusion is the most common cause of hospitalization and a frequent indirect cause of mortality in patients on chronic hemodialysis. The clinical assessment of an arteriovenous shunt is presently the most widely adopted method for the diagnosis of vascular access occlusion in hemodialysis patients, but no studies have yet investigated objectively its sensitivity and positive predictive value (PPV). Continuous-wave (CW) Doppler ultrasound is a simple, inexpensive, and noninvasive technique for the assessment of arterial blood flow. We have carried out a prospective evaluation of the PPV of CW Doppler for the diagnosis of vascular access occlusion in hemodialysis patients and compared it with clinical investigation. Methods: Fourty-one hemodialysis patients with clinical diagnosis of occlusion of their fistula were studied, and in 23 of them the diagnosis of occlusion was objectively validated. Results: CW Doppler in the patients in whom occlusion was objectively validated showed PPV of 86 and 83% under basal conditions and after fistula compression, respectively, with sensitivities of 95 and 100%, respectively. Clinical diagnosis, under the same conditions, showed a PPV of 83% and a sensitivity of 100%. Conclusions: CW Doppler and clinical examination have a similar high sensitivity for the diagnosis of occlusion of the dialysis access; thus, there is no need to use routinely Doppler CW examination, unless objective documentation is required.