Objective: Preterm infants are more likely to have episodes of abdominal distention, emesis, and gastric residuals 24 hours after their first screening examination for retinopathy of prematurity (ROP) than on the day preceding the examination. Because these feeding problems reflect abnormalities in motor function, the purpose of this study was to compare antral and duodenal motor activity and gastric emptying in preterm infants before and after the instillation of mydriatics. Study design: Using a low compliance continuous perfusion manometric system, we recorded antral and duodenal fasting motor activity in 11 preterm infants before and after the instillation of mydriatics for their first screening examination for ROP. Gastric emptying was compared before and after the eye examination. Results: Although the number of antral motor contractions remained relatively constant throughout the study, duodenal motor contractions decreased nearly fourfold after the instillation of mydriatics versus that seen before (P <.01). Gastric emptying was significantly delayed after the completion of the eye examination compared with that seen before the examination (P <.05). Conclusion: Current doses of mydriatics inhibit duodenal motor activity and delay gastric emptying, and these gastrointestinal effects of mydriatics may underlie the feeding difficulties seen in preterm infants on the day of screening examinations for ROP. (J Pediatr 2000;137:327-30)