It is essential to start enteral nutrition early to preterm infants by giving small amounts of milk (preferably human milk) to ensure that metabolic homeostasis is kept stable and to limit postnatal growth retardation. Increasing feeding volumes to reach "full enteral feeding" is limited by individual feeding tolerance. Feeding intolerance is extremely common in premature infants. The most frequent signs of a suspect feeding intolerance are the presence of gastric residuals, abdominal distension and the onset of crises of apnea/bradycardia. Gastric residuals are probably a benign consequence of delayed gut maturation and motility in VLBW infants and there are no established normal standards. When gastric aspirates occur isolated they should not immediately induce the neonatologist to withhold feeding. Gastric residual becomes more important when accompanied by other warning signs, such as bilious vomiting, abdominal distension, abdominal wall erythema or ecchymosis, gross or occult blood in the stool, apnoea, bradycardia and temperature instability. Nutrition protocols in preterm infants must take caution when starting and increasing enteral feeding, and pay proper, but not excessive, attention to early signs of food intolerance.