The effect of premedication with the cholinergic blocking drugs, atropine and glycopyrronium, was investigated in two groups, each of twenty patients, with regard to their effects on cardiac rate and rhythm during induction of anaesthesia and tracheal intubation. Another similar group of twenty patients was given no anticholinergic premedication. The incidence of dysrhythmias was 35% in the atropine group and 10% in the glycopyrronium group but there were no dysrhythmias in patients given no anticholinergic drug. The average rises in arterial pressure were similar in all three groups. Atropine administration led to a greater initial rise in heart rate before the induction of anaesthesia, although the average heart rates were similar in the three groups at the time of intubation and cuff inflation. The routine use of anticholinergic premedication seems to be unnecessary since the antisialogogue effect does not make any difference to the course of anaesthesia. However, if the antisialogogue action is important, glycopyrronium offers an advantage over atropine.