Fifteen infants recovering from neonatal respiratory disease had arterial blood gases and lung mechanics measured 5 minutes before bolus feeds and at 5, 10, 20, and 30 minutes after feeding to determine physiologic effects of feeding. PaO2 fell significantly from prefeeding values at 5, 10, and 20 minutes after feeds. Mean prefeeding pH and base excess values were significantly different from mean postfeeding values at 5, 10, 20, and 30 minutes, respectively. PaCO2 remained unchanged before and after feeding. Heart rate and systolic and diastolic blood pressure did not change throughout the study. Dynamic lung compliance, respiratory, rate, and tidal volume did not change significantly but there was a trend toward increase in tidal volume. Mean minute volume rose with time as a consequence of the increased tidal volume. Work of breathing remained unchanged at 10 and 20 minutes postfeed and increased slightly at 30 minutes; this was due to a small increase in both elastic and viscous work components at this time.