Glycopyrrolate, an anticholinergic agent that does not cross the blood-brain barrier, has several indications, but its mydriatic effect has never been tested. This study was carried out in order to compare the mydriatic effect of glycopyrrolate 0.5% to that of atropine sulfate 1%.Glycopyrrolate 0.5% and atropine 1.0% were instilled separately in the eyes of albino rabbits. Pupil diameter and intra-ocular pressure were monitored.Mydriasis was noted within 5 min of glycopyrrolate instillation, reached near-maximal level at 15 min and persisted for 1 week. Glycopyrrolate 0.5% showed a faster, stronger and more persistent mydriatic effect than atropine 1.0%. Administration of glycopyrrolate 0.5% solution b.i.d. for 1 week did not affect intra-ocular pressure or produce any adverse reaction.Glycopyrrolate solution has the potential to deliver an ocular anticholinergic effect without causing associated central anticholinergic hazards.