The effectiveness of calcium chloride in asystole has been challenged; retrospective studies have not supported its use. We conducted a prospective, randomized, blinded study comparing the effectiveness of calcium chloride with saline in the prehospital paramedic setting. Seventy-three patients who had received epinephrine, bicarbonate, and atropine and were in refractory asystole were included in the study, which was conducted from October 1982 to October 1983. Traumatic and pediatric arrests were excluded. The successful resuscitation rate was three of 39 in the calcium group versus one of 34 in the saline group (P less than .37). A successful resuscitation was defined as the conveyance of a patient with a pulse and a rhythm to an emergency department. Groups were analyzed for sex, age, and witnessed arrests. There was no statistically significant difference between the groups. No patient who was resuscitated successfully in the field was discharged from the hospital alive. We conclude that calcium chloride is not of value in resuscitating patients from refractory asystole in the prehospital cardiac arrest setting.