OBJECTIVE: To determine the safety and efficacy of glycopyrrolate in the treatment of developmentally disabled children with sialorrhea. DESIGN: Placebo-controlled, double-blind, crossover dose-ranging study. SETTING: Outpatient facilities in 2 pediatric hospitals. PATIENTS: Thirty-nine children with both developmental disabilities and excessive and bothersome sialorrhea. MAIN OUTCOME MEASURES: Parent and investigator evaluation of change in sialorrhea and adverse effects. RESULTS: Glycopyrrolate in doses of 0.10 mg/kg per dose is effective at controlling sialorrhea. Even at low doses, 20% of children may exhibit adverse effects severe enough to require discontinuation. CONCLUSIONS: Glycopyrrolate is effective in the control of excessive sialorrhea in children with developmental disabilities. Approximately 20% of children given glycopyrrolate may experience substantial adverse effects, enough to require discontinuation of medication. Arch Pediatr Adolesc Med. 2000;154:1214-1218.