Out-of-hospital cardiac arrests were studied in Israel from 1984 to 1985. More than 3,500 patients in cardiac arrest received paramedic care. Eighty-three percent of cases were caused by underlying heart disease. Overall, 17% of patients with arrest caused by heart disease were admitted and 7% were discharged from the hospital. There was a wide variation in the percent discharged among the 15 paramedic service areas, ranging from 0% to 13%. Factors associated with successful resuscitation included witnessed collapse, rhythm of ventricular fibrillation, short interval from collapse to cardiopulmonary resuscitation (CPR) and delivery of advanced cardiac life support, collapse at public location, and bystander initiation of CPR. Improvements in survival are likely to result if CPR is more frequently and promptly initiated and the time to arrival of definitive paramedic care can be improved.