From April 2000 to November 2002, the Department of Health (England) placed 681 automated external defibrillators (AEDs) in 110 public places for use by volunteer lay first responders. An audit has been undertaken of the first 250 deployments, of which 182 were for confirmed cardiac arrest. Of these, 177 were witnessed whilst 5 occurred in situations that were remote or initially inaccessible to the responders. The response interval between collapse and the initiation of CPR or AED placement was estimated to be 3-5 min in most cases. Ventricular fibrillation or rapid ventricular tachycardia (one case) was the first recorded rhythm in 146 cases (82%). In all, 44 of the 177 witnessed cases are known to have survived to hospital discharge (25%). Complete downloads are available for 173 witnessed cases and of these 140 were shocked: first-shock success, defined as termination of the fibrillatory waveform for 5 s or more, was achieved in 132 of them. When data quality permitted, the downloads were analysed with special reference to the numbers of compressions given and also to interruptions in compression sequences for ventilations, for rhythm analysis by the AED, for clinical checks, and for unexplained operator delays. The average rate of compressions during sequences was 120 min(-1), but because of interruptions, the actual number administered over a full minute from the first CPR prompt was a median of only 38. The speed of response by the lay first responders in relation to AED use was similar to that reported for healthcare professionals.