The effect of barbiturates on cardiac rate and rhythm during halothane ancsthesia without intubation was studied in a triple‐blind, randomized trial with 28 patients. The test group was premedicated with pentobarbital and induced with thiopental, while the control group was anesthetized with halothane and nitrous oxide only. There was a significant preponderance of sinus‐bradycardia and supraventricular disturbances in the control group. It is concluded that the use of barbiturates is advantageous because of their ability to suppress enhanced vagal tone.