The two anticholinergics, atropine and glycopyrrolate, were used for premedication and as an adjunct to reversal of residual neuromuscular block in a double-blind study. Glycopyrrolate, being about twice as potent as atropine in the clinical situation, was used in half the dosage of atropine. When used for premedication, no difference was found between the drugs concerning patients complaining of dry mouth, but more patients in the glycopyrrolate group had a gastric juice pH greater than 2.5 compared to the atropine group (not statistically different). The reversal mixture consisted of necostigmine 2.5 mg with either atropine 1 mg or glycopyrrolate 0.5 mg. The heart rate response between 2 and 10 min after injecting the reversal mixture was statistically significant (P ranged from 0.0001 to 0.05), the atropine group showing the most marked decrease: 18% in the atropine group had sinus bradycardia compared to 5% in the glycopyrrolate group: 34% in the atropine group exhibited arrhythmias compared to 10% in the glycopyrrolate group, the most common form being a nodal rhythm in both groups. More patients in the atropine group had "excessive" oropharyngeal secretions (more than 2 ml) when extubated (P less than 0.05). The postoperative assessment showed little difference in the two groups, apart from a lower incidence of nausea and vomiting in the atropine group (not statistically different). The study shows that the use of glycopyrrolate was associated with a more stable cardiovascular system, fewer arrhythmias and superior control of oropharyngeal secretions at the time of reversal.