For six months a survey was made of all the patients in the Nottingham District Health Authority who died or who were brought to hospital after a cardiac arrest outside hospital. During this period just under half of the emergency ambulance shifts were covered by specially trained crews with defibrillators. During the study period the ICD coding of death certificates indicated that 894 (25%) of the 3575 deaths were due to ischaemic heart disease. During this period the ambulance service received 17,749 emergency calls, which included 445 patients who had cardiac arrests outside hospital. One hundred and forty seven of these patients were carried by ambulances equipped with defibrillators and resuscitation was attempted in 83. Seven patients survived to leave hospital. The special ambulance service was cost effective--a simple calculation suggests that the cost per life saved was approximately 2600 pounds, but it seems unlikely that special ambulance services will materially affect community fatality rates from ischaemic heart disease.