Because of a report of necrotizing enterocolitis and death of a neonate from cyclopentolate eyedrops, we prospectively studied the effects of cyclopentolate 0.5% and 0.25% ophthalmic solutions and of a placebo on gastric volume and acid secretions in 20 pre-term infants. Placebo and cyclopentolate 0.25% eyedrops had no significant effect on the tested gastric functions. However, cyclopentolate 0.5% eyedrops significantly decreased gastric acid secretion and volume. Since this effect may predispose to the development of gastroenteritis, we recommend that cyclopentolate 0.5% be avoided in preterm infants; a weaker concentration of cyclopentolate eyedrops, however, can be used for mydriasis.