Glycopyrrolate 5 and 7.5 micrograms kg-1 and atropine 10 and 15 micrograms kg-1 were studied in 80 paediatric patients to assess more fully the dose of glycopyrrolate required for adequate prevention of the oculocardiac reflex. A dose-related improvement in protection from this reflex was seen with both drugs, but neither drug prevented reductions in heart rate in every patient. A nodal rhythm was the most common arrhythmia observed with both drugs. In the doses used, no adverse effects were noted and no further anticholinergic treatment was required during muscle traction. Higher doses may be associated with an increase in side-effects with more pronounced dryness of the mouth and tachycardia and, with atropine, a greater likelihood of the production of the "central anticholinergic syndrome".