Enteral nutrition support is used extensively in the care of infants and children, both for acute and chronic conditions. Monitoring a child's tolerance of enteral feedings is an ongoing challenge. Monitoring routines vary significantly between institutions, practitioners, and patient settings, and a number of definitions are used for "intolerance." Some guidelines have scientific basis and others are passed along in a more anecdotal fashion. This review describes commonly used monitors for tolerance to enteral nutrition for infants and children and discusses pertinent data relevant to practice.