BACKGROUND: Time to cardiopulmonary resuscitation (CPR) is a main determinant of survival after out-of-hospital cardiac arrest. Only widespread implementation of training courses for laypersons can decrease response time. METHODS AND RESULTS: In this prospective randomized trial, we evaluated how laypersons retained CPR skills and skills in using the automated external defibrillator (AED). A total of 1095 volunteers were randomly assigned to receive CPR/AED-training courses of 2h (375 persons), 4h (378 persons) or 7h (342 persons) duration. Courses were held in accordance with the guidelines for CPR. All trainees were tested immediately after the initial class in a standardized test scenario using an AED and a manikin. Either at 6 or at 12 months, retests were given to 164 and 206 volunteers, respectively. In 479 volunteers, retesting was completed at both 6- and 12-month intervals. At the immediate tests, the 7-h training group showed a slightly higher rate of correct responses (7h: 96%, 4h: 94%, 2h: 92%) (p
