A newly developed procedure for total cardiac denervation employing cryosurgical techniques is described. Thirty-three dogs underwent cryosurgical cardiac denervation. Twenty-seven survived the procedure and were divided into three groups. Completeness of denervation was evaluated by recording hemodynamic responses to sodium nitroprusside-induced hypotension, phenylephrine-induced hypertension, and direct cardiac autonomic nerve stimulations acutely (group I, n = 11) and 2 weeks after denervation (group II, n = 5). Serial drug infusion studies were performed during an 8-month period in group III animals (n = 11). Myocardial biopsies for catecholamine content were done in groups II and III. Both direct and reflex hemodynamic responses to autonomic neural stimulation were abolished in the acutely denervated hearts. Furthermore, at 2 weeks, direct neural stimulation was without effect, and myocardial catecholamine content was 95% depleted (p < 0.001). Serial drug infusion studies revealed a changing spectrum of responses, suggesting the onset of reinnervation by 8 months following the procedure. Myocardial catecholamfine content was 85% depleted at that time (p < 0.001). Cryo-surgical cardiac denervation is an effective technique offering the advantages of safety, simplicity, and completeness.