Abstract Background: The Public Access Defibrillation (PAD) Trial was a randomized, controlled trial designed to measure survival to hospital discharge following out‐of‐hospital cardiac arrest (OOH‐CA) in community facilities trained and equipped to provide PAD, compared with community facilities trained to provide cardiopulmonary resuscitation (CPR) without any capacity for defibrillation. Objectives: To report the implementation of community‐based lay responder emergency response programs in 1,260 participating facilities recruited for the PAD Trial in the United States and Canada. Methods: This was a descriptive study of the characteristics of participating facilities, volunteers, and automated external defibrillator (AED) placements compiled by the PAD Trial, and a qualitative study of factors that facilitated or impeded implementation of emergency lay responder programs using focus groups of PAD Trial site coordinators. Results: The PAD Trial enrolled 1,260 community facilities (14.8% residential), with 20,400 lay volunteers (mean ± standard deviation = 13.4 ± 10.7 per facility) trained to respond to OOH‐CA. The 598 locations randomized to receive AEDs required 2.7 ± 1.8 AEDs per facility. Volunteer attrition was high, 36% after two years. Barriers to recruitment and implementation included identification of appropriate “at‐risk” facilities, lack of interest or fear of litigation by a facility key decision maker, lack of motivated potential volunteer responders, training and retraining resource requirements, and lack of an existing communication/response infrastructure. Conclusions: These data indicate that implementation of community‐based lay responder programs is feasible in many types of facilities, although these programs require substantial resources and commitment, and many barriers to implementation of effective PAD programs exist.