Intermittent doses of suxamethonium have been known to result in bradycardia changes in cardiac rhythm. In order to assess the efficacy of a newer quaternary ammonium antimuscarinic, glycopyrrolate, on the cardia effects of intermittent suxamethonium, 28 patients received this drug intravenously just before induction of anesthesia. For comparison, 28 other patients were given atropine. In the atropine series, three patients developed bradycardia while none of those of the glycopyrrolate series did so. In addition, more patients had cardiac arrhythmias in the atropine group. Although no statistically significant differences were seen, clinically, glycopyrrolate seems to afford better protection against the cardiac changes resulting from intermittently administered suxamethonium.