Milk flow achieved during feeding may contribute to the ventilatory depression observed during nipple feeding. One of the important determinants of milk flow is the size of the feeding hole. In the first phase of the study, investigators compared the breathing patterns of 10 preterm infants during bottle feeding with two types of commercially available (Enfamil) single-hole nipples: one type designed for term infants and the other for preterm infants. Reductions in ventilation, tidal volume, and breathing frequency, compared with prefeeding control values, were observed with both nipple types during continuous and intermittent sucking phases; no significant differences were observed for any of the variables. Unlike the commercially available, mechanically drilled nipples, laser-cut nipple units showed a markedly lower coefficient of variation in milk flow. In the second phase of the study, two sizes of laser-cut nipple units, low and high flow, were used to feed nine preterm infants. Significantly lower sucking pressures were observed with high-flow nipples as compared with low-flow nipples. Decreases in minute ventilation and breathing frequency were also significantly greater with high-flow nipples. These results suggest that milk flow contributes to the observed reduction in ventilation during nipple feeding and that preterm infants have limited ability to self-regulate milk flow.