Automated external defibrillators (AED) have been recommended for use in outpatient dialysis clinics to improve outcomes from cardiac arrest, the most common cause of death in patients with ESRD. The effectiveness of this policy is unknown. The study cohort consisted of 43,200 hemodialysis patients in the US Gambro Healthcare System from 2002 to 2005. Of these, 729 patients who sustained an in-center cardiac arrest were identified. Baseline characteristics at the time of the event were compared between patients who underwent hemodialysis in clinics with and without an AED on site. Unadjusted survival and survival adjusted for potential confounders was measured using Cox proportional hazards regression models. Unadjusted survival at 30 d was 19 versus 15% (P = 0.12) and 9.5 versus 7.8% at 1 yr (P = 0.39) in the AED-present and AED-absent groups, respectively. AED presence was not associated with outcome in unadjusted analysis (hazard ratio [HR] 0.91; 95% confidence interval [CI] 0.78 to 1.07; P = 0.26). Univariable analysis identified age (HR 1.07 per decade; 95% CI 1.01 to 1.13), serum albumin (HR 0.91 per 0.7-mg/dl increase; 95% CI 0.82 to 1.01), and indwelling dialysis catheters (HR 1.21; 95% CI 1.02 to 1.42) as potential confounders. Medications including angiotensin-converting enzyme inhibitors or angiotensin receptor blockers, beta blockers, calcium channel blockers, other BP medications, aspirin, antibiotics, and antiarrhythmics were associated with survival and considered confounders. After controlling for case mix and confounders, AED presence was not associated with outcome (HR 0.98; 95% CI 0.82 to 1.18; P = 0.83). Presence of AED in the dialysis clinic is not sufficient by itself to improve the abysmal outcome from in-clinic cardiac arrest in hemodialysis patients in the United States.